A  CONCISE 
HISTORY  OF  CHEMISTRY 


A  CONCISE 
HISTORY  OF  CHEMISTRY 


BY 

T.   P.   HILDITCH 

B.Sc.  (LOND.),  A.I.C. 


WITH   SIXTEEN   DIAGRAMS 


NEW  YORK 
D.  VAN  NOSTRAND   COMPANY 

23   Murray  and   27  Warren  Streets 
1911 


PREFACE 

THIS  book  is  an  attempt  to  outline  as  briefly  and 
succinctly  as  possible  the  historical  development 
of  chemistry,  and  is  designed  more  especially  for  those 
students  whose  interest  in  this  aspect  of  the  science  is 
stimulated  by  the  inclusion  of  "  Historical  Chemistry  " 
in  the  syllabus  of  examinations  which  concern  them.  It 
is  therefore  presumed  that  the  reader  is  simultaneously 
acquiring,  or  already  possesses,  a  fair  knowledge  of 
present-day  chemical  theory  and  practice,  and,  accord- 
ingly, no  space  is  devoted  to  the  actual  explanation  of 
hypotheses  or  reactions  except  in  so  far  as  the  latter  are 
directly  bound  up  with  the  historical  sequence  of  facts. 

Whenever  practicable,  each  section  is  arranged  so  that 
it  follows  approximately  those  lines  upon  which  a  student 
would  learn  the  simple  chemical  facts  in  question ;  thus, 
the  introductory  chapters  dealing  with  the  older  chemistry 
(down  to  Lavoisier)  are  succeeded  by  the  history  of 
elements  and  inorganic  compounds,  treated,  as  far  as 
possible,  according  to  the  Periodic  Law,  whilst  the  details 
of  other  branches,  such  as  organic  and  physical  chemistry, 
follow  in  general  the  order  given  in  the  standard  text- 
v  books.  Many  facts,  important  in  themselves  but  not  so 
germane  to  the  general  development  of  ideas,  have  been 
collected  in  tabular  form  for  convenient  reference,  and  the 

235538 


vi  A  SHORT  HISTORY  OF  CHEMISTRY 

book  is  concluded  by  a  summary  of  the  work  of  some 
notable  chemists  and  a  chronological  survey  of  the  ex- 
perimental and  theoretical  advances  in  chemistry  during 
the  last  two  centuries.  In  order  to  secure  a  more  com- 
pact volume,  no  detailed  references  have  been  given  to 
the  literature  in  which  the  discoveries,  theories,  etc.,  were 
published,  but  the  dates  given  in  all  cases  will  assist  the 
student  to  obtain  the  original  account  of  any  particular 
point  desired. 

I  wish  to  acknowledge  the  kind  help  I  have  received 
from  Dr.  A.  E.  Dunstan,  who  read  the  book  in  manu- 
script ;  from  Dr.  S.  Smiles,  Dr.  A>  W.  Stewart,  and  Mr. 
H.  J.  Page,  who  aided  in  the  correction  of  proofs ;  and 
from  Prof.  J.  N.  Collie,  F.R.S.,  who  advised  me  with 
respect  to  the  arrangement  of  certain  parts  of  the  work. 

T.  P.  HILDITCH 
UNIVERSITY  COLLEGE 

UNIVERSITY  OF  LONDON 


CONTENTS 

CHAPTER  I 

PAGE 

THE  EVOLUTION  OF  THE  SCIENCE i 

i.  The  Chief  Chemical  Epochs,  i.  2.  The  Origin  of  the  Science 
and  its  Name,  3.  3.  Alchemy :  the  Ennobling  of  Metals,  6. 
4.  Alchemy :  Medicinal,  9.  5.  The  Beginnings  of  Modern 
Inductive  and  Experimental  Method,  n.  6.  Chemistry  in 
the  Phlogistic  Period,  12. 

CHAPTER  II 
THE  CHEMICAL  HISTORY  OF  FIRE,  AIR,  AND  WATER    ...      14 

i.  Fire  and  the  "  Fire  Principle,"  14.  2.  Air :  a  Mixture  of  Gases, 
16.  3.  Air:  its  Constituents,  18.  4.  Air:  its  "Inactive" 
Constituents,  21.  5.  Water,  23.  6.  Fire:  Lavoisier's  Re- 
volution, 24. 

CHAPTER  III 
THE  ULTIMATE  CONSTITUTION  OF  MATTER 27 

i.  Ancient  and  Alchemical  Views,  27.  2.  The  Evolution  of 
Chemical  Nomenclature,  30.  3.  Discovery  of  Combining 
Proportions,  32.  4.  Dalton's  Atomic  Theory,  33.  5.  De- 
velopment of  the  Atomic  Hypothesis,  35.  6.  The  Periodic 
System,  38.  7.  Is  all  Matter  derived  from  one  ultimate 
Fundamental  Material  ?  41. 

CHAPTER  IV 

INORGANIC    COMPOUNDS    AND    THE    LAWS    OF    CHEMICAL    COM- 
BINATION  45 

i.  Chemical  Affinity  and  the  Manner  of  Chemical'  Combination, 
45.    2.  The  Structure  of  Organic  Compounds,  48.    3.  Val- 
ency, 51.    4.  Electro-chemical  Theories,  56. 
b  vii 


viii          A  SHORT  HISTORY  OF  CHEMISTRY 
CHAPTER  V 

PAGE 

NOTES  ON  THE  HISTORY  OF  THE   ELEMENTS  AND  THEIR   CHIEF 

COMPOUNDS 59 

i.  Acidic  Oxides,  59.  2.  Basic  Oxides  and  Metallic  Salts,  62. 
3.  Mineralogy,  65.  4.  The  Chemical  Elements,  68.  5.  The 
Metals  of  the  Rare  Earths,  73.  6.  Radio-active  Elements,  74. 

CHAPTER  VI 
THE  HISTORY  OF  ORGANIC  CHEMISTRY 76 

i.  Organic  Chemistry :  the  Chemistry  of  Animate  Nature,  76.  2. 
The  Earlier  Theories  of  Structure  of  Organic  Compounds,  77. 

3.  Saturation  Capacity  and  the  Modern  Structure  Theory,  86. 

4.  Benzene   and  the   Cyclic    Compounds,  88.     5.  Dynamic 
Isomerism,    100.      6.    Steric   Hindrance,    105.      7.    Stereo- 
isomerism :    (a)   Geometrical    Isomerism,    107.      8.   Stereo- 
isomerism:  (b)  Optical  Isomerism,  in. 

CHAPTER  VII 
COMPOUNDS  AND  REACTIONS  IN  ORGANIC  CHEMISTRY    .        .        .117 

i.  Hydrocarbons,  117.  2.  Oxygen  Derivatives:  (a)  Hydroxylic 
Compounds,  119.  3.  Oxygen  Derivatives :  (b)  Carbonyl 
Compounds,  Reactions  of  Condensation,  121.  4.  Oxygen 
Derivatives:  (c)  Carboxylic  Acids,  122.  5.  Oxygen  Deriva- 
tives: (d)  Ketonic  Acids,  126.  6.  Nitrogen  Derivatives,  127. 
7.  Derivatives  of  Elements  other  than  Oxygen  or  Nitrogen, 
129.  8.  Heterocyclic  Compounds,  131. 

CHAPTER  VIII 
THE  CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      ....    137 

i.  Chemical  Processes  in  the  Vegetable  and  Animal  Kingdoms, 
137.  2.  The  Alkaloids,  139.  3.  The  Terpenes,  140.  4. 
Sugars  and  other  Carbohydrates,  142  ;  Glucosides,  142.  5. 
Amido  Acids,  Proteins  and  Purines,  145.  6.  Fermentation 
and  Enzyme-Action,  152. 


CONTENTS  ix 

CHAPTER  IX 

PAGE 

THE  APPLICATION  OF  CHEMISTRY  TO  MANUFACTURES  .        .        .     154 

r.  The  Preparation  of  Useful  Elements:  Metallurgy,  155.  2. 
The  Alkali,  Sulphuric  Acid,  Vinegar  and  similar  Industries, 
158.  3.  Some  recent  Electro-Technical  Methods,  162.  4. 
Glass,  Earthenware,  and  Cements,  163.  5.  Paper,  Matches, 
Heat,  and  Light,  165.  6.  Dyes,  167.  7.  Explosives,  170. 

CHAPTER  X 

THE  HISTORY  OF  PHYSICAL  CHEMISTRY 172 

i.  The  Physical  Chemistry  of  Gases,  172.  2.  Crystallography, 
175.  3.  Solutions,  176.  4.  Molecular  Weight  Determina- 
tion, 179.  5.  Relation  of  Physical  Properties  to  Chemical 
Constitution  :  (a)  Mechanical,  181.  6.  Relation  of  Physical 
Properties  to  Chemical  Constitution  :  (b)  Electrical,  184.  7. 
Relation  of  Physical  Properties  to  Chemical  Constitution :  (c) 
Optical,  185.  8.  Photo-chemistry,  187.  9.  Thermo-chemistry, 
189.  10.  Electro-chemistry,  191.  n.  Chemical  Statics  and 
Dynamics,  192.  12.  The  Phase  Rule,  195. 

CHAPTER  XI 
THE  PROGRESS  OF  EXPERIMENTAL  METHOD 197 

i.  Improvements  in  Chemical  Apparatus,  197.  2.  Improvements 
in  Chemical  Methods,  198.  3.  Development  of  Analytical 
Methods,  201.  4.  The  Determination  of  Atomic  Weights, 
206. 

APPENDIX  A 
BIOGRAPHICAL  INDEX  OF  CHEMISTS 209 

Alchemical  Period,  209.  Phlogistic  Period,  210.  Modern 
(Fundamental)  Period,  212.  Modern  (Static  Structural) 
Period,  215.  Modern  (Dynamic  Structural)  Period  (Arranged 
Alphabetically),  222. 

APPENDIX  B 

CHRONOLOGICAL  SUMMARY  OF  CHEMICAL  EVENTS  OF  OUTSTANDING 

INTEREST 229 

INDEX  OF  NAMES 247 

INDEX  OF  SUBJECTS 259 


A    CONCISE 
HISTORY    OF    CHEMISTRY 

CHAPTER  I 
THE  EVOLUTION  OF  THE  SCIENCE 

§  i.  The  Chief  Chemical  Epochs— History  of  any  kind 
may  be  recorded  in  either  of  two  ways  : — 

(1)  Chronologically,  as  a  whole; 

(2)  By  taking  one   section   of  the  subject  at  a  time  and 
treating  each  separate  division  chronologically. 

The  first  alternative  is  usually  employed  in  the  case  of,  for 
example,  a  country  or  province,  while  the  second  would  be  neces- 
sary in  dealing  with  a  continent  composed  of  a  variety  of  races, 
each  with  its  own  life-story.  We  shall  find  it  advisable  to  adopt 
this  latter  plan  with  regard  to  chemistry,  for  the  science  nowadays 
possesses  so  many  branches  and  ramifications  that  it  is  very 
much  easier  to  understand  the  evolution  of  the  whole  from  a 
consideration  of  the  development  of  the  various  individual  parts. 
There  are,  nevertheless,  certain  well-marked  epochs  which  should 
be  noticed  in  the  general  progress  of  the  science. 

It  is  certain  that  no  civilized  race  has  yet  existed  in  the 
world  without  giving  some  thought  to  the  properties  and 
mutual  relations  of  the  various  sorts  of  terrestrial  matter.  Of 
course,  no  one  can  tell  precisely  where,  when,  and  how  chemistry 
really  came  into  existence,  and  it  would  not  suit  our  present 
purpose  to  discuss  the  matter  at  any  length.  '  Let  it  suffice  to 
say  that  remote  Chinese  and  Hindu  philosophers  appear  to 
have  paid  attention  to  this  branch  of  science,  while  our  records 
i 


2  A     HORT  HISTORY  OF  CHEMISTRY 

go  back  with  certainty  to  the  times  of  the  ancient  Egyptians 
and  Greeks.1  These  devoted  themselves  to  speculations  about 
the  ultimate  composition  of  natural  substances,  and  at  the  same 
time — notably  in  Egypt — the  idea  of  the  transmutation  of 
metals  began  to  develop.  The  predominance  of  this  notion 
at  about  the  commencement  of  the  fourth  century  A.D.  marks  the 
close  of  the  first  or  Ancient  Period — the  period  of  philosophic 
speculation — and  the  opening  of  the  second,  the  Alchemical 
Epoch.  This  lasted  for  more  than  a  thousand  years,  and  it  is 
said  that  even  in  the  last  century  there  yet  existed  individuals 
holding  alchemical  tenets ;  practically  speaking,  however,  the 
ideals  of  chemists  underwent  a  profound  change  towards  the 
close  of  the  seventeenth  century.  Alchemists  were  dominated 
by  two  pre-conceived  and  extraordinary  ideas :  firstly,  that  it 
was  possible  to  change  common  metals  into  gold  by  a  chemical 
process ;  secondly,  that  the  change  was  to  be  accomplished  by 
I  the  agency  of  a  substance,  known  variously  as  The  Essence, 
'  The  Philosopher's  Stone,  The  Elixir  of  Life,  etc.,  which  pos- 
sessed entirely  supernatural  powers. 

The  development  of  the  physical  sciences,  on  the  other 
hand,  had  been  uncommonly  rapid  during  the  seventeenth 
century,  and  this  was  largely  due  to  the  adoption  of  induc- 
tive methods.  It  is  thus  easy  to  see  how  chemists,  tired  of 
fruitless  search  on  a  vain  quest,  and  sickened  by  the  duplicity 
which  was  too  frequently  practised,  turned  to  new  methods. 
Robert  Boyle  in  particular  changed  the  trend  of  chemical 
reasoning,  and  thereby  rendered  his  greatest  service  to  science. 
In  the  next  period — the  Phlogistic  Period,  dating  from  about 
1700  to  1775 — the  properties  of  the  most  various  bodies  were 
examined  with  a  view  to  classification.  The  property  which 
attracted  most  attention  was  that  of  combustion — so  much  so 
that  this  era  fittingly  takes  its  name  from  the  famous  but  incor- 
rect theory  designed  to  explain  the  phenomenon  of  burning. 

1  Berthelot's  "  Les  Origines  d' Alchemic  "  is  a  standard  work  for  those 
wishing  to  study  in  detail  the  earliest  era  of  the  science. 


THE  EVOLUTION  OF  THE  SCIENCE  3 

In  1777  Lavoisier  published  his  theory  of  combustion,  worked 
out  by  the  help  of  the  balance,  and  made  possible  by  Scheele's 
and  Priestley's  discoveries  of  oxygen  ;  this  inaugurated  the  era 
of  modern  chemistry,  which  may  again  be  subdivided  into  three 
periods  : — 

(1)  The   Fundamental  Period,   comprising   the   labours   of 
Davy,  Dalton,    Gay-Lussac,   Berzelius,  Dulong,  Faraday,  etc. 

(2)  The  Period  of  Static  Structural  Chemistry,  commencing 
with  Wohler's  synthesis  of  urea  in  1828,  and  comprising  the 
foundations  of  systematic  organic  and  physical  chemistry. 

(3)  The  Period  of  Dynamic  Structural  Chemistry,  i.e.  the 
development  of  the  most  recent  views  concerning  the  ultimate 
composition   of  matter,    the  structure  of  chemical  (and  par- 
ticularly   "  organic ")    compounds,    the  nature  of  electrolysis, 
etc.     This   period   may   be  said   to  have  commenced  about 
1880. 

We  may,  then,  summarize  the  six  periods  of  chemical  history 
in  the  table  on  page  4,  giving  at  the  same  time  instances  of 
familiar  historical  events  which  may  serve  in  some  measure 
to  correlate  the  various  dates. 

§  2.  The  Origin  of  the  Science  and  its  Name— There 
are  various  indications  that  some  knowledge  of  the  practical 
applications  of  chemistry  existed  long  before  the  era  of  Western 
civilization.  The  Chinese,  for  instance,  possessed  means  of 
manufacturing  articles  which  in  some  cases  cannot  be  made  with 
the  same  degree  of  elegance  at  the  present  day  ;  this  implies  a 
considerable  acquaintance  with  some  sort  of  technical  chemistry. 
At  a  less  indefinite  date,  which  is  still  too  remote  to  be  fixed 
with  any  certainty,  we  find  the  Phoenicians  and  Egyptians  well 
acquainted  with  the  manufacture  of  glass  and  pottery  ;  some  of 
the  simpler  metallurgical  processes  were  already  practised,  in- 
cluding the  mechanical  separation  of  gold,  the  smelting  of  iron, 
the  preparation  of  mercury  from  cinnabar,  anjd  the  separation  of 
lead  and  silver.  The  arts  of  dyeing  and  embalming  were  also  1 1 
largely  engaged  in  by  the  Egyptians.  The  Jews,  too,  in  the x  ' 


A  SHORT  HISTORY  OF  CHEMISTRY 


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THE  EVOLUTION  OF  THE  SCIENCE  5 

reign  of  Solomon  (and  probably  for  some  time  prior  to  that 
period)  rec  jgnized  at  least  six  distinct  metals  :  gold,  silver,  iron, 
copper,  tin,  and  lead. 

Metallurgy  at  this  early  date  was  carried  on  chiefly  in  the 
northern  part  of  Egypt ;  deposits  of  ores  were  fairly  abundant 
in  that  region,  and,  in  addition,  the  seaport  of  Alexandria 
afforded  means  for  the  import  of  ores  from  the  various  lands 
washed  by  the  Mediterranean.  Not  infrequently  metallic  de- 
posits, consisting  of  a  mixture  of  metals  or  ores,  would  be 
found  ;  sometimes  much  lead  accompanied  by  a  little  silver, 
sometimes  silver  and  gold  together,  sometimes  other  metallic 
mixtures.  Moreover,  methods  were  soon  devised  for  preparing 
the  "noble"  from  the  "base"  materials  in  such  instances; 
what  is  more  natural,  then,  than  that  the  idea  of  the  baser 
being  transformed  into  the  rarer  metals  should  gradually  come 
into  the  minds  of  these  early  metal-workers?  Here  is  the 
origin  of  the  transmutation  theory  ;  gold  and  silver  were  re- 
garded, then  as  ever,  as  most  precious  and  valuable  ;  mixtures 
of  these  with  common  substances  were  found — perhaps  Nature 
was  slowly  transforming  the  base  into  the  rare  ?  This  sugges- 
tion developed  into  a  most  persistent  and  dominating  belief  in 
the  alchemical  period ;  and  even  now,  centuries  after  the 
theory  has  been  dropped,  we  retain  in  common  use  phrases 
which  betray  an  innate  leaning  towards  alchemical  ideas,  such 
as  "  base  "  and  "  noble"  metals,  "perfect  "  gases,  etc. 

The  famous  transmutation  theory,  then,  probably  arose  from 
a  very  superficial  kind  of  reasoning,  and  this  may  be  due  to  the 
circumstance  that  the  early  metallurgists  do  not  appear  as  a 
rule  to  have  been  in  touch  with  the  "  philosophers  "  or  learned 
theorists.  The  latter  class  of  men,  naturally  most  prominent 
in  ancient  Greece,  had  little  in  common  with  the  former. 

It  is  convenient  to  summarize  at  this   point  the  chemica 
knowledge  of  the  ancients : — 

(i)  Practical. — In  China  and  India  (?),  in  Phoenicia  and 
Egypt :  metallurgy,  dyeing,  glass,  earthenware. 


6  A  SHORT  HISTORY  OF  CHEMISTRY 

(2)  Theoretical. — In  Greece  (500-200  B.C.)  and  Rome  (100 
B.C.-A.D.  150);  vague,  general  observations  on  nature. 

(3)  Experimental  (according  to  the  modern  meaning  of  the 
word). — Practically  none. 

With  regard  to  the  origin  of  the  word  "  chemistry,"  there  is 
a  choice  of  about  six  very  plausible  "  derivations,"  such  as  from 
the  North  Egyptian  word  "  chemi "  =  Egypt  ;  from  ^  77  //,  c  t  a  = 
Egyptian  art;  from  x  >///,€  to,  =  black,  etc.  As  these  cannot 
all  be  correct,  let  us  be  content  merely  to  say  that  the  first  use 
of  the  word  "  chemia  "  appears  in  an  astrological  treatise  com- 
piled by  Julius  Firmicus,  a  writer  of  the  fourth  century  of  the 
Christian  era. 

§  3.  Alchemy :  the  Ennobling  of  Metals — When  we  turn 
to  review  the  next  period  of  chemical  history,  it  at  first  appears  as 
if  the  Greeks  had  all  the  clear-sighted  theories  and  the  alche- 
mists none,  for  the  superabundance  of  views  and  metaphor  are 
bewildering.  There  is  a  break  of  some  200  years  between  the 
latest  philosophical  writings  and  the  earliest  authentic  alche- 
mical works,  and  during  this  time  a  great  change  in  view-point 
took  place,  culminating  in  the  predominant  belief  in  "  trans- 
mutation," which  appears  as  a  well-known  doctrine  in  all  the 
latter  treatises,  although  it  is  scarcely  mentioned  in  the  former. 
This  is  natural  in  view  of  the  probable  origin  of  the  theory 
(p.  5)  and  of  the  fact  that  the  old  philosophy  finally  died  out 
after  Hypatia's  murder,  and  was  replaced  by  a  system  based  on 
the  Christian  religion.  The  unscrupulous  blending  of  Christian 
hypotheses  and  natural  science  led  to  as  dismal  consequences 
to  both  as  the  intolerance  of  Christian  authorities  to  science 
has  done  in  many  an  instance.  Assuming  that  they  possessed 
by  revelation  a  divine  "  scheme  "  of  the  moral  universe,  the 
new  race  of  thinkers  extended  it  to  the  material  world,  and 
deduced  that  simplicity  was  the  key-note  and  perfection  the 
end  of  matter  as  well  as  of  mind.  Gold  and  silver  were  as- 
sumed the  most  perfect  metals,  "  the  end  of  Nature  in  regard 
to  metals,"  and  the  original  aim  of  alchemy  was  to  "assist 


THE  EVOLUTION  OF  THE  SCIENCE  7 

Nature "  by  the  application  of  certain  agents  or  medicines, 
which,  acting  on  the  "  baser  "  metals,  should  purge  away  the 
impurities  and  leave  worthier  members  of  the  metallic  state. 
Much  later  the  idea  arose  that  such  agents — especially  the 
greatest  of  all,  the  Philosopher's  Stone,  Alkahest,  Elixir,  etc. — 
ought  to  be  of  service  to  men's  as  well  as  metals'  ills;  and 
iatro-chemistry,  in  which  chemistry  is  looked  upon  as  the 
servant  of  medicine,  was  developed.  This  branch  of  alchemy, 
and  the  alchemical  theories  of  the  ultimate  constitution  of 
matter,  are  discussed  later  (pp.  9,  28). 

Because  of  the  universal  desire  for  gold  and  silver,  and  the 
ease  of  making  alloys  or  amalgams  bearing  strong  superficial 
resemblance  thereto,  the  aim  which  alchemists  set  before  them, 
albeit  at  first  purely  philosophical,  naturally  lent  itself  to  decep- 
tion, and  alchemy  quickly  became  degraded  into  a  mere  gold- 
imitating  art.  Various  popes  and  princes  therefore  proscribed 
its  practice  in  their  realms,  but  usually  found  it  too  valuable 
a  means  of  filling  empty,  purses  to  be  very  severe  on  its  adepts. 
Consequently  nearly  every  European  court  had  its  private 
alchemist,  who  in  general  was  merely  a  swindler,  not  a  scientist, 
with  whom  matters  went  hard  in  case  of  detection,  but  who 
usually  found  it  sufficiently  easy  to  secure  against  such  a  con- 
tingency and  to  make  a  comfortable  living.  For  a  long  while, 
indeed,  true  chemists  were  few  and  far  between,  till  better  ideals 
once  more  arose,  thanks  in  the  main  to  the  outspoken  utter- 
ances of  Boyle,  Kunkel,  and  others.  With  -the  charlatans  we 
are  not  concerned,  but  proceed  to  summarize  as  far  as  we  can 
the  general  trend  of  theory — a  difficult  task,  since,  to  a  greater 
extent  than  at  any  other  period,  each  followed  his  own  in- 
dependent path. 

Nearly  all  alchemical  writers  refer  to  one  Hermes  Trismegis- 
tus  as  the  father  or  originator  of  alchemy.  This  somewhat 
mythical  person  was  supposed  to  have  developed  very  largely  the 
practical  side  of  alchemy  in  Egypt  at  an  indefinitely  remote 
period ;  his  existence  (except  in  the  minds  of  these  writers)  is  a 


8  A  SHORT  HISTORY  OF  CHEMISTRY 

matter  of  doubt,  but  his  name  has  certainly  survived,  even  in  the 
chemical  parlance  of  the  present  day.  It  is  amusing  to  note 
how,  later  on,  devotees  of  the  "  hermetic  art "  in  their  anxiety 
to  invest  their  science  with  a  touch  of  religious  sanctity  asserted 
that  the  first  of  their  cult  were  Biblical  characters,  such  as  Adam, 
Tubal-Cain  ("  an  instructor  of  every  artificer  in  brass  and  iron  "), 
Moses  and  Miriam,  or  Job  ("  Thou  shalt  lay  up  gold  as  dust  ") ! 
In  reality  the  science  of  alchemy  was  chiefly  fostered  in  the 
museum  of  Alexandria  l  in  the  first  centuries  of  our  era,  under 
both  heathen  and  Christian  teachers,  as  Zosimos  of  Panopolis 
(circa  A.D.  420-450)  and  Bishop  Synesius  (circa  A.D.  400)  until 
the  decay  of  the  Western  Roman  Empire  and  the  advent  of  the 
Arabs,  i.e.  until  about  A.D.  640.  The  Arabs  took  up  science 
with  wonderful  zeal,  for  within  a  century  universities,  which 
soon  became  famed  for  mathematics,  medicine,  astronomy,  and 
alchemy,  began  to  spring  up  in  Bagdad,  Cordova,  Seville,  Toledo, 
and  elsewhere,  and  to  these  in  the  course  of  the  next  four  cen- 
turies came  many  Western  European  students.  Geber  is  the 
first  alchemist  of  note  whose  existence  is  authentic,  and  of  his 
actual  life  we  know  very  little,  except  that  he  was  an  Arab 
physician,  whose  reputation  lasted  down  through  the  Middle 
Ages.  No  other  Mohammedan  alchemist  attained  such  fame  as 
he,  and  he  wrote  several  works  on  chemistry,  which  still  exist  in 
the  form  of  Latin  translations.  When  Arab  learning  declined 
(about  1200)  alchemy  was  propagated  in  England,  France,  and 
Germany  by  the  students  mentioned  above,  and  indeed  was 
fully  developed  in  Western  Europe  by  the  year  1400.  It  was 

1  The  "  Alexandrian  Academy  "  was  founded  as  a  school  and  library 
by  Ptolemy  Soter,  destroyed  by  fire  in  47  B.C.  and  A.D.  216,  and  taken  by 
the  Arabs  in  642.  It  is  interesting  because  (i)  it  must  have  acted  as  a 
point  of  contact  for  Greek  theorists  and  Egyptian  metal-workers,  (2)  it  was 
the  final  seat  of  the  old  heathen  philosophy,  and  although  the  Christian 
authorities  murdered  the  latest  of  the  philosophers,  Hypatia,  in  their  jeal- 
ous endeavours  to  stamp  it  out,  enough  of  their  writings  must  have  been 
left  to  enable  the  Arabs,  some  two  hundred  years  later,  to  assimilate  and 
propagate  science  as  known  to  Hypatia,  and  her  disciples. 


THE  EVOLUTION  OF  THE  SCIENCE  9 

carried  on  notably  in  "apothecaries'  shops,"  which,  designed 
for  the  purpose  of  preparing  the  simple  medicines  then  used, 
served  also  to  train  numbers  of  keen  alchemists. 

The  fact  that  chemistry  in  the  Middle  Ages  was  dominated 
by  mediaeval  religion  will  account  for  many  of  the  biassed, 
prejudiced  ideas  which  held  sway,  and  the  influence  of  the 
desire  to  make  gold  and  the  belief  in  the  possibility  of  trans- 
mutation all  helped  to  enshroud  the  real  end  of  the  science  in  a 
mist  of  preconceived  notions  and  a  tangle  of  hopeless  beliefs. 
Yet  it  must  not  be  supposed  that  this  period  of  chemistry  was 
unfruitful.  Indeed  it  has  been  very  well  said  that  the  hunt  for 
the  Philosopher's  Stone  and  unlimited  gold  resembled  very  much 
the  search  of  the  sons  of  the  man  who  said  on  his  deathbed 
that  there  was  a  fortune  buried  in  his  vineyard — and  we,  the  des- 
cendants of  the  alchemists,  are  still  reaping  the  benefit  from  the 
fertile  discoveries  these  made  in  the  course  of  so  much  mis- 
directed ploughing. 

§  4.  Alchemy :  Medicinal — While  the  philosopher's  mind 
was  fixed  on  one  theme — gold  manufacture — his  experiments 
were  naturally  concerned  only  with  metallic  derivatives,  so  that 
few  of  the  new  facts  discovered  related  to  any  but  this  class 
of  compounds.  When  the  Renaissance  of  learning  and  the 
Reformation  led  to  a  wider  intellectual  outlook  the  scope  of 
chemists'  views  also  appeared  to  broaden,  and  a  larger  field  of 
use  for  chemistry  was  opened  up.  Originally  the  doctrine  of 
the  ennobling  of  metals  had  been  deduced  by  analogy  (however 
fanciful)  with  human  moral  development,  and  now,  conversely, 
the  beliefs  (for  theories  were  to  alchemists  "articles  of  faith") 
which  had  arisen  as  to  the  composition  of  metals  were  applied 
to  the  healing  of  physical  disease.  Basil  Valentine  and  a  few 
other  workers  of  the  first  alchemical  period  here  and  there 
applied  isolated  metallic  preparations  as  medicinal  remedies,  but 
Paracelsus  (sixteenth  century)  was  the  first  to  emphasize  the 
close  inter-dependence  and  alliance  of  chemistry  and  medicine. 
He  assumed  that  the  three  "  principles,"  sulphur,  salt,  and 


ib  A  SHORT  HISTORY  OF  CHEMISTRY 

mercury,  which  were  held  to  constitute  the  different  metals, 
also  composed  the  human  body,  and  that  illness  was  the  result 
of  deficiency  or  excess  of  one  or  more  of  these  in  the  organism 
— an  assumption  which  was  characteristically  accepted  as  a 
creed  by  Sylvius,  van  Helmont,  Tachenius  and  other  alchemists 
of  the  next  few  generations.  The  "  medicine  of  the  third 
order,"  the  Philosopher's  Stone,  which  should  bring  perfection 
to  weak  and  erring  metals,  was  naturally  supposed  to  perform 
the  same  function  for  mortals,  endowing  them  with  an  indefinite 
span  of  life  and  resistance  to  all  physical  decay.  This  fusion 
of  medicine  and  chemistry  was  of  advantage  to  both,  but  par- 
ticularly to  the  latter,  which  then  attracted  men  of  wider 
culture  than  previously  ;  it  led  to  the  discovery,  too,  of  further 
new  facts  and  compounds,  especially  in  the  domain  of  what  is 
now  "  organic  "  chemistry,  and  unintentionally  paved  the  way 
for  the  emancipation  of  chemistry  from  a  gold-making  art  to  a 
truth-seeking  science. 

At  the  present  day  there  exist  in  nearly  all  civilized  coun- 
tries societies  for  the  extension  of  chemical  science  and  numer- 
ous periodicals  devoted  to  the  same  purpose  ;  but  in  alchemical 
times  there  was  nothing  of  this  kind,  and  the  isolated  character 
of  each  individual's  work  is  very  conspicuous.  (Cf.  Appendix, 
pp.  209,  210.) 

In  the  earlier  history  of  alchemy  this  independence  was  due 
to  the  selfish,  competitive  motives  aroused  by  the  quest  for 
gold  and  the  Philosopher's  Stone.  Later  on  the  change  to 
iatro-chemical  ideals,  which  postulated  health  for  all  rather  than 
wealth  for  one,  and  the  repeated  failures  to  obtain  the  "  elixir," 
which  aroused  a  feeling  that  united  work  might  solve  problems 
which  baffled  isolated  workers,  caused  the  formation  of  various 
alchemical  unions.  These  were  chiefly  "  secret  societies/'  and 
they  thrived  from  about  the  beginning  of  the  seventeenth  to  the 
middle  of  the  eighteenth  century,  but  were  in  no  way  compar- 
able to  or  connected  with  the  real  scientific  societies  then 
existing,  such  as  the  Royal  Society  of  London  (founded  1663). 


THE  EVOLUTION  OF  THE  SCIENCE  ti 

Alchemy  consisted,  then,  in  the  later  stages  of  its  existence, 
of  two  branches,  the  one  concerned  merely  with  gold  manufac- 
ture, the  other  with  the  application  of  chemistry  to  healing. 
The  latter  side  of  the  subject  cannot  be  said  to  have  been 
abandoned,  but  rather  to  have  been  extended  by  the  rapid 
adoption  of  the  inductive  method  of  research,  its  development 
in  one  direction  (the  phenomena  of  combustion)  leading  to  the 
doctrine  of  phlogiston,  which  characterized  the  next  period  of 
chemical  history.  The  efforts  to  make  gold  from  baser  metals 
were  so  unsuccessful,  and  yet  afforded  such  scope  for  duplicity 
and  charlatanism,  that  a  great  deal  of  scepticism  arose  in  course 
of  time  as  to  the  possibility  of  metal-transmutation  at  all,  and 
gradually  the  idea  died  out.  It  might  be  pointed  out  that, 
until  definite  proof  was  given  for  regarding  the  metals  as  ele- 
ments (i.e.  in  Lavoisier's  time),  it  was  not  chemically  wrong  to 
believe  in  the  possibility  of  changing  one  into  another. 

§  5.  The  Beginnings  of  Modern  Inductive  and  Ex- 
perimental Method — One  of  the  first  to  apply  the  "  induc- 
tive "  method  to  chemistry  was  Roger  Bacon  (thirteenth 
century) ;  then,  towards  the  end  of  the  seventeenth  century, 
the  necessity  of  putting  aside  the  subsidiary  aims  which  chem- 
istry might  serve  seems  to  have  been  more  widely  felt,  and  the 
efforts  of  chemists  were  directed  along  new  lines,  notably  by 
the  work  of  Boyle  and  Kunkel.  The  latter,  himself  an  enthu- 
siastic alchemist,  was  concerned  more  particularly  with  the 
careless  phraseology  and  frequent  duplicity  of  his  contempo- 
raries, and  denounced  both  with  considerable  vigour.  Boyle's 
writings,  however,  show  that  he  had  little  faith  in  alchemy,  but 
possessed  views  on  the  nature  of  chemical  combination  and  of 
chemical  elements  which  have  stood  their  ground  ;  moreover 
— and  this  is  very  noteworthy — he  stated  that  experimental 
methods  and  careful  observation  were  the  only  sure  paths  to 
development.  The  general  adoption  of  these  views,  although 
hampered  for  a  time  by  neglect  of  quantitative  investigation, 
has  undoubtedly  been  the  cause  of  the  rapid  progress  of  the 
science  to  its  present  position. 


12  A  SHORT  HISTORY  OF  CHEMISTRY 

Let  us  contrast,  then,  the  three  different  methods  of  investi- 
gation which  we  have  now  discussed. 

The  ancients  based  their  theories  on  careful  observation  of 
natural  phenomena,  but  made  no  experiments  to  shed  further 
light  on  their  assumptions. 

The  alchemists  based  their  theory  on  one  fundamental 
assumption  (the  simplicity  and  unity  of  nature),  and  made 
many  experiments  to  show  that  the  theory  was  certainly  true. 

The  modern  inductive  method,  which  chemists  owe  especi- 
ally to  Boyle,  is  to  base  a  theory  on  a  consideration  of  the 
known  facts,  thence  to  design  new  experiments  to  throw  fresh 
light  on  the  subject,  and,  from  the  new  facts  so  discovered,  to 
modify  or  confirm  the  original  theory,  and  then  repeat  the 
process  indefinitely. 

The  whole  difference  of  the  systems  lies  in  the  different 
relations  which  the  various  ages  assigned  to  the  bearing  of  ex- 
periment and  observation  on  theory. 

§  6.  Chemistry  in  the  Phlogistic  Period — It  has  been 
necessary  to  give  a  detailed  account  of  the  chemistry  of  the 
alchemists  and  ancients,  because  their  view-points  differed 
fundamentally  from  those  of  all  later  investigators.  Chemistry, 
indeed,  as  understood  at  present,  originated  when  alchemy  de- 
cayed and  the  attainment  of  chemical  truth  was  made  the  goal 
of  the  science.  The  phlogistic  chemists  form  a  kind  of  link 
between  old  and  modern  workers,  for  they  aimed  at  the  ex- 
tension of  chemical  knowledge,  while  their  theories  and  methods 
were  often  not  far  in  advance  of  those  of  their  predecessors, 
the  alchemists.  We  will  therefore  conclude  this  sketch  of 
chemical  evolution  by  a  resume  of  the  work  done  by  the 
phlogistonists,  and  then  pass  on  to  the  history  of  the  various 
branches  of  chemistry. 

In  the  phlogistic  period  we  notice  first  of  all  that  qualitative 
investigation  was  the  almost  invariable  rule — the  use  of  the 
balance  being  quite  exceptional.  The  chief  subject  of  experi- 
ment was  the  phenomenon  of  combustion,  usually  explained 


THE  EVOLUTION  OF  THE  SCIENCE  13 

at  that  time  on  the  "phlogiston"   hypothesis    (cf.   chap,  ii., 

P-   15)- 

Much  progress  was  also  made  with  methods  of  qualitative  an- 
alysis, and  during  this  epoch  the  composition  of  water  (Caven- 
dish) and  of  air  (Mayow,  Priestley,  Scheele,  etc.)  was  cleared 
up.  In  consequence  of  the  manipulative  processes  intro- 
duced by  Boyle  and  (in  lesser  degree)  the  later  iatro-chemists, 
the  investigation  of  gases  went  on  rapidly  and  the  isolation  of 
nitrogen  or  "  phlogisticated  air  "  (Rutherford,  Scheele,  Priestley), 
oxygen  or  " dephlogisticated  air"  (Scheele,  Priestley),  car- 
bon dioxide  or  "  fixed  air  "  (Black),  hydrogen  (Cavendish),  and 
chlorine  (Scheele)  among  other  gases  may  be  placed  to  the 
credit  of  the  "  phlogistic  "  chemists.  The  mutual  relationship  of 
salts,  acids  and  bases  was  also  recognized,  Rouelle  (1744)  de- 
fining the  former  as  a  combination  of  the  two  latter,  and  also 
distinguishing  between  neutral,  acidic,  and  basic  salts.  The 
more  ordinary  acids  became  fairly  well-known,  sulphuric,  phos- 
phoric, nitric,  and  hydrochloric  acids  being  classified  as  "  mineral 
acids,"  while  formic,  citric,  oxalic,  uric,  tartaric  and  others  were 
termed  "  animal  acids  " ;  bases  such  as  the  alkalies  and  alkaline 
carbonates,  and  "  earths  "  such  as  the  calces  of  magnesia  alba, 
alum,  barytes,  quartz,  etc.,  were  also  characterized  at  about 
this  time.  In  what  is  now  called  organic  chemistry,  the  pre- 
paration of  alcohol,  wood  spirit  and  various  "  ethers  "  was 
advanced,  while  Scheele,  who  discovered  most  of  the  "  animal 
acids  "  just  mentioned,  also  isolated  glycerine  from  fats. 

Technical  chemistry  now  rose  to  be  an  independent  branch 
of  the  science,  the  following  being  the  more  notable  develop- 
ments of  the  period :  the  manufacture  of  nitric,  sulphuric,  and 
Nordhausen  sulphuric  acid  ;  the  metallurgy  of  zinc,  and  pro- 
cesses for  gilding  and  silvering  metals ;  the  fabrication  of  por- 
celain (Sevres) ;  and  of  mineral  dyes  and  paints,  such  as  Prussian 
blue  (Fe4"i[Fe"(CN)6]3)  and  Scheele's  green, 


CHAPTER  II 

THE  CHEMICAL  HISTORY  OF  FIRE,  AIR,  AND 
WATER 

§  i.  Fire  and  the  "Fire  Principle  "—Of  the  four  "Aris- 
totelian elements  "  it  may  be  said  that,  while  chemists  always 
have  been  and  will  be  concerned  with  the  constituents  of  earth, 
the  nature  of  fire,  air,  and  water  was  practically  cleared  up  in 
the  course  of  a  century,  or,  more  precisely,  during  the  phlogis- 
tic period.  It  is  thus  convenient  to  study  these  three  together 
at  this  point.  It  was  the  universal  custom  of  the  ancient 
philosophers  to  consider  all  three  as  elements,  but  it  must  be  re- 
membered that  "  element  "  at  that  period  meant  rather  a  funda- 
mental property,  than  a  fundamental  unitary  kind  of  matter. 
Later  on,  some  of  the  alchemists  held  that  by  interaction  of  pairs  of 
these  four  elementary  properties,  three  fundamental  principles, 
akin  to  mercury,  sulphur,  and  salt,  were  formed.  It  is  easy  to  see 
why  "  fire  "  was  given  a  position  equal  to  the  other  three  elements, 
for  while  the  gaseous,  liquid,  and  solid  states  could  be  repre- 
sented fundamentally  by  air,  water,  and  earth,  the  equally  patent 
state  of  "flame"  was  supposed  to  be  the  manifestation  of  the 
principle  of  "  fire  ". 

The  earlier  alchemists  did  not  turn  their  attention  very 
seriously  to  the  problem  of  combustion,  but  in  the  iatro-chemical 
era,  Sylvius  (circa  1650)  suggested  that  sulphur  (the  alchemical 
"  principle  ")  was  the  principle  of  fire,  and  also  drew  attention 
to  the  analogy  between  burning  and  breathing.  This  suggestion 
was  accepted  by  other  alchemists,  such  as  Homberg  and  Kun- 
kel ;  Boyle,  who,  to  use  the  title  of  one  of  his  works,  was  more  of 

14 


THE  CHEMICAL  HISTORY  OF  FIRE  15 

a  "  sceptical  chymist,"  regarded  it  as  possible,  but  not  proved,  and 
preferred  merely  to  call  the  fire  principle  a  "  combustible  earth  ". 

In  the  meantime  Mayow  (1668-9)  showed  that  there  was 
a  substance  in  air  which  took  part  both  in  the  calcination  of 
metals  and  in  respiration,  but  did  not  seemingly  pursue  the 
subject  far  enough  to  give  a  complete  explanation.  At  about 
the  same  date  the  alchemist  Becher  was  trying  to  revive  the 
old  "  principles  "  under  new  names,  "  mercurial,  vitreous,  and 
combustible  earths  " ;  the  latter,  "  terra  pinguis,"  was  set  free 
when  combustion  or  calcination  took  place.  Unfortunately,  as 
has  frequently  happened,  preconceived  assumption  met  with 
more  notice  than  precise  observation  (due  in  this  case  to 
Mayow),  and  Stahl,  one  of  Becher's  pupils,  elaborated  Becher's 
idea  into  the  famous  phlogiston  theory. 

Stahl  assumed  that  all  combustible  or  calculable  matter  con- 
tained a  substance  "phlogiston  " *  which  was  evolved  during 
the  process  of  burning  ;  the  more  readily  and  completely  com- 
bustible the  substance,  then,  the  greater  was  the  amount  of 
phlogiston  it  contained.  Coal  was  supposed  to  be  particularly 
rich  in  phlogiston,  for  on  heating  it  is  almost  entirely  burnt 
away,  while  by  heating  it  with  many  metal  oxides  the  metal  is 
reformed.  On  the  other  hand,  the  metals,  etc.,  were  supposed 
to  be  the  products  of  union  of  phlogiston  with  the  metal  calces, 
and  we  can  represent  these  views  by  an  equation,  perhaps,  as 
follows  : — 

Metal  ^  Phlogiston  +  metal  calx  (oxide). 
Sulphur  ^t  Phlogiston  +  sulphuric  acid. 
Phosphorus  ^>  Phlogiston  +  phosphoric  acid. 

When  a  calx  or  sulphuric  or  phosphoric  acid  is  heated  with 
matter  rich  in  phlogiston  (coal),  the  metal  or  sulphur  or  phos- 
phorus is  "  revived  ".  This  idea  is  a  direct  inversion,  so  to 
speak,  of  our  modern  view  of  combustion,  for  we  hold  that 

1  Some  consider  that  "  phlogiston  "  has  been  in  a  manner  realized  in 
the  form  of  the  "  heat  of  formation  or  decomposition  "  of  a  body. 


1 6  A  SHORT  HISTORY  OF  CHEMISTRY 

addition  of  oxygen  takes  place  in  combustion,  and  elimination 
of  oxygen  in  reduction.  In  order  to  make  the  relation  of 
phlogistic  to  modern  views  quite  clear,  we  may  add  that : — 

Elimination  of  phlogiston  =  oxidation  (combustion). 

Addition  of  phlogiston  =  reduction  (elimination  of  oxygen). 

Stahl  suggested  that  a  similar  explanation,  based  on  phlogiston, 
could  be  found  for  respiration,  which  would  thus  consist  of  an 
exhalation  of  phlogiston. 

This  theory  gave  a  concise  explanation  of  a  large  number  of 
miscellaneous  facts,  and  it  was  exceedingly  simple.  Unfor- 
tunately, it  was  also  hopelessly  impossible ;  the  "  elimination  of 
phlogiston  "  was  invariably  accompanied  by  gain  in  weight,  and 
conversely !  This  did  not  deter  the  earlier  adherents  of  the 
theory,  at  all  events,  from  accepting  it  as  blindly  as  did  the 
alchemists  the  doctrines  of  metal  transmutation  and  the  exist- 
ence of  the  elixir  of  life.  One  cannot  quite  understand  the 
attitude  of  chemists  who  said  that  "  although  "  gain  in  weight 
always  accompanied  combustion,  and  loss  in  weight  what  we 
now  call  reduction,  yet  "  notwithstanding  this  "  the  former  phe- 
nomenon was  due  to  loss,  and  the  latter  to  gain,  of  phlogiston. 
Of  course  little  attention  was  paid  at  that  time  to  quantitative 
methods,  and  the  importance  of  mass  as  the  only  reliable  guide 
to  the  "  amount  of  matter  in  a  substance  "  was  unrealized  ;  but 
even  much  later,  phlogistonists  suggested,  as  a  way  out  of  the 
difficulty,  that  their  fire-stuff  possessed  a  negative  weight. 

That  the  phlogistic  theory  was  in  no  wise  a  worthless  attempt 
at  an  explanation  of  combustion  is  proved  by  the  number  of 
useful  discoveries  made  in  all  departments  of  chemistry  in  the 
-  eighteenth  century  and  by  the  men  whose  allegiance  to  it  did 
not  prevent  them  from  being  brilliant  chemists  (Black,  Cavendish, 
Priestley,  Scheele,  Bergman,  etc.).  The  nature  of  air  and  water, 
indeed,  was  finally  elucidated  during  this  epoch,  and  it  will  be 
most  convenient  to  deal  with  these  before  proceeding  tO;give  a  de- 
scription of  the  advent  of  Lavoisier  and  the  decline  of  phlogiston. 

§  2.  Air:   a  Mixture  of  Gases — For   long  ages  people 


THE  CHEMICAL  HISTORY  OF  AIR  17 

were  content  with  the  old  notion  that  air  was  an  "  element," 
a  simple  substance,  but  in  course  of  time  two  circumstances 
combined  to  render  this  view  open  to  question. 

(1)  Van  Helmont,  whom  many  regard  as  the  "  founder  of 
pneumatic  chemistry,''  showed  that  it  was  possible  to  isolate" 
gases  from  various  materials,  and  that  these  gases  frequently 
possessed  varying  properties.     He,  indeed,  was  the  first  to  use 
the  term    "  gas  "  (geist  =  spirit),  and   differentiated    "  gases," 
which  he  supposed  to  be  unliquefiable,  from    "  vapours,"  or 
gases  which  on   cooling  condensed  to  the  liquid  state.     He 
seems  to  have  isolated  carbonic  acid  in  various  ways   (com- 
bustion,   fermentation,    etc.),   and  gave   specific   names   to   a 
number  of  other  gases,  but  we  cannot  tell  in  many  cases  to 
which  particular  substance  he  refers. 

(2)  A   little   later    (1650-90)    the   behaviour   of  substances 
heated  in  an  enclosed  volume  of  air  began  to  be  observed ; 
Mayow    (1668-9)    noted   that    when  metals  were  calcined  or 
animals  breathed,  a  part  of  the  air  (the  " spiritus  nitro-areus" 
also  a  constituent  of  saltpetre)  was  used  up,  while  the  remainder 
("  nitrous  air  ")  was  somewhat  lighter  than  the  original  air,  was 
insoluble  in  water  and  did  not  support  combustion.     Similarly 
Boyle's  work  on  calcination  and  respiration  showed  him  that 
air  was  a  mixture  and  that  only  one  part  of  it  was  actually  essen- 
tial to  burning  or  breathing,  but  neither  he  nor  Mayow  definitely 
prepared  this  active  ingredient. 

The  fact  that  air  itself  is  ponderable  was  first  proved  by  Rey 
(1630).  These  facts  comprise  practically  the  whole  knowledge 
of  air  down  to  the  middle  of  the  eighteenth  century.  The 
phlogistonists  regarded  it  simply  as  a  receptacle  into  which 
phlogiston  escaped  in  cases  of  combustion,  etc.,  and  if  it  was 
desired  to  explain  the  incapability  of  some  gases  to  support 
life  or  flame,  did  so  by  the  assumption  that  such  were  already 
"  phlogisticated," — saturated  with  phlogiston.  Little  material 
progress  was  made  till  later  upholders  of  the  phlogistic  theory 
(Black,  Priestley,  Scheele,  etc.)  devised  means  for  separating, 


1 8  A  SHORT  HISTORY  OF  CHEMISTRY 

collecting,  and  manipulating  gases  which  rendered  their  more 
minute  investigation  possible.  Priestley,  for  instance,  introduced 
the  familiar  "pneumatic  trough  "  and  "beehive  shelf"  and  also 
utilized  mercury,  instead  of  water,  as  the  collecting  medium. 
We  may  thus  say  that  at  about  1750  air  was  believed  to  be  a 
mixture  of  at  any  rate  two  ingredients,  one  which  supported  life 
and  one  which  did  not,  or  was  a  gas  "  partly  saturated  with 
phlogiston  ". 

§  3.  Air :  its  Constituents — The  bulk  of  the  work  of  the 
later  phlogistonists  on  air  was  of  a  qualitative  nature,  but  excep- 
tions are  to  be  noticed  in  the  case  of  Joseph  Black's  work  on 
carbonic  acid  (1750-5)  and  Cavendish's  analysis  of  air  and 
water  (1785  onwards).  The  crucial  point  of  the  problem  was 
reached  when  Scheele  and  Priestley  simultaneously  and  inde- 
pendently discovered  oxygen  in  the  summer  of  1774.  Both  of 
these  were  examining  the  gases*'  evolved  from  the  "  calces " 
of  metals  under  different  conditions,  and  both  obtained  oxygen 
by  heating  red  oxide  of  mercury,  and  noted  that  it  supported 
combustion  similarly  to  air,  only  very  much  more  vigorously. 
Their  adherence  to  the  phlogiston  theory  prevented  them  from 
arriving  at  the  correct  explanation  of  combustion,  but  they  re- 
cognized that  air  was  a  mixture  of  two  different  gases.  Scheele 
also  obtained  the  new  gas  by  heating  saltpetre  alone,  and  by 
warming  black  oxide  of  manganese  with  phosphoric  or  sulphuric 
acids  ;  he  called  it  fire  air.  Priestley  obtained  it  from  minium 
(Pb3O4)  as  well  as  from  mercuric  oxide,  and  named  it  de- 
phlogisticated  air,  from  the  readiness  with  which  it  "  absorbed 
phlogiston  ".  By  finding  an  absorbent  for  the  new  gas  (Priestley 
(1775)  used  "saltpetre  gas,"  nitric  oxide,  and  Scheele  (1777) 
ferrous  hydrate  or  phosphorus)  both  proceeded  to  isolate  the 
other  constituent  of  air  in  a  tolerably  pure  state,  and  found  it 
to  be  somewhat  lighter  than  air  and  a  non-supporter  of  com- 
bustion, thus  confirming  Mayow's  previous  work  (p.  15);  it 
should  be  noted  that  the  existence  of  oxygen  itself  was  practically 
discovered  by  Mayow  and  by  Boyle,  although  neither  succeeded 


THE  CHEMICAL  HISTORY  OF  AIR  19 

in  its  isolation.  This  inactive  part  of  the  air,  which  Priestley 
termed  phlogisticated  air,  and  Scheele  spent  air,  had  also  been 
isolated  a  little  earlier  (1772)  by  Rutherford,  who  adhered  to 
Mayow's  name,  nitrous  air.  A  number  of  other  scientists  also 
worked  on  this  gas  at  about  this  period,  and  it  acquired  a  variety 
of  names,  Fourcroy  in  1788  and  Berthollet  in  1791  showed  it 
was  a  constituent  of  animal  tissues,  and  the  former  author,  from 
its  relation  to  the  "  alkaline  "  ammonia,  suggested  the  name 
alcaligkne  ;  Lavoisier  used  the  term  mephitic  air  and  later  azote 
— a  name  which  means  the  same  as  the  German  Stickstoff  (suffo- 
cating substance).  Its  modern  name,  nitrogen,  was  first  used 
by  Chaptal,  on  account  of  its  relation  to  nitre.  It  should  be 
noted  that  the  elementary  character  of  the  gas  was  not  realized 
at  this  time,  nor  indeed  for  a  considerable  period  after,  for  Davy 
and  Berzelius  believed  it  to  be  made  up  of  oxygen  and  another 
element — a  view  which  was  not  finally  abandoned  till  about  1 820. 

We  must  now  consider  the  other  constituents  of  air — carbonic 
acid,  water,  and  the  "  rare  gases  of  the  atmosphere  ". 

The  presence  of  carbonic  acid  was  appreciated  even  before 
Mayow's  time,  for  van  Helmont  (early  part  of  the  seventeenth  cen- 
tury) noticed  its  occurrence  in  air,  in  caves,  in  mineral  springs, 
and  in  animal  organs,  and  showed  how  to  prepare  it  by  burning 
coal,  fermenting  wine  or  decomposing  chalk  or  "  potashes  "  with 
vinegar.  He  called  it  gas  sylvestre,  but  confused  it  with  other 
gases  which  do  not  support  combustion.  Black  (1750-5) 
also  realized  its  presence,  and  called  it  fixed  air,  but  we  must 
discuss  his  work  somewhat  later,  as  it  is  concerned  with  the  com- 
position of  the  alkalies  and  alkaline  carbonates  rather  than  with 
that  of  air.  Lavoisier  (1775-6)  and  Dalton  (1803)  both  deter- 
mined with  more  or  less  accuracy  the  proportions  of  carbon 
and  oxygen  present  in  the  gas,  but  this  we  can  also  deal  with 
more  appropriately  in  a  later  chapter.  We  should  mention, 
however,  that  Scheele  and  Priestley  each  showed  that  when  a 
candle  burns  in  an  enclosed  air-space,  exactly  as  much  fixed  air 
is  generated  as  dephlogisticated  air  is  consumed. 


A  SHORT  HISTORY  OF  CHEMISTRY 


It  has  already  been  said  that  Cavendish  was  one  of  the  few 
chemists  of  the  phlogistic  period  who  concerned  themselves 
with  quantitative  research,  and  as  a  matter  of  fact,  he  made 
some  exceedingly  accurate  analyses  of  air,  showing  that  its  com- 
position was  practically  constant,  but  varied  within  very  small 
limits.  He  estimated  the  oxygen  by  explosion  with  hydrogen, 
and  then  to  see  if  the  residual  phlogisticated  air  was  homogene- 
ous, sparked  it  with  excess  of  oxygen  till  no  further  contraction 
took  place.  He  stated  (1785)  that  "  if  there  is  any  part  of  the 
phlogisticated  air  of  our  atmosphere  .  .  .  which  differs  from 
the  rest  ...  we  may  safely  conclude  that  it  is  not  more  than 
TJT_  part  of  the  whole  ".  A  hundred  and  ten  years  later  it  was 
proved  by  Lord  Rayleigh  and  Professor  Ramsay  that  a  little  less 
than  one  per  cent  of  the  atmosphere  was  made  up  of  a  series 
of  "  inactive,"  chemically  inert,  gases.  We  will  summarize  the 
knowledge  of  air  gained  by  the  end  of  the  phlogistic  period  and 
then  return  to  the  description  of  these  "new  "  gases:— 


PERIOD  : 

Ancient,  Al- 
chemical. 


& 


Modern 
Name. 
Oxygen 


Definitely 

Isolated. 

1774 


Nitrogen  1772 


PHLOGISTIC. 


Phlogistic  Names.  Regarded  as  — 

Fire  air  (Scheele)  Air 

Dephlogisticated  air  devoid  of 

(Priestley)  phlogiston. 
Spiritus  nitro-asreus 

(Mayow) 

Spent  air  (Scheele)  Air 

Phlogisticated  air  saturated  with 

(Priestley)  phlogiston 
Nitrous  air  (Mayow)  (Priestley),  or 

Mephitic  air,  Azote  Nitric  acid 

(Lavoisier)  saturated  with 

Nitrogen  (Chaptal),  phlogiston 

etc.  (Cavendish). 


Carbonic  acid  About  1620  Gas  sylvestre  (van 
or  earlier       Helmont) 

Fixed  air  (Black) 


Water 


Various,  e.g. 

Phlogisticated 

muriatic, 

nitric,  or 

sulphuric  acid, 

An  elemc. 


THE  CHEMICAL  HISTORY  OF  AIR         .    21 

§  4.  Air :  its  "  Inactive  "  Constituents— The  history  of 
the  five  "  inactive  gases  of  the  atmosphere  "  is  comprised  within 
a  very  recent  period — the  last  fifteen  years  ;  and  much  of  the 
work  of  their  discovery,  curiously  enough,  was  carried  out  within 
a  few  hundred  yards  of  the  house  in  Gower  Street,  London,  in 
which  Cavendish,  the  last  previous  worker  on  the  subject,  lived 
a  century  before.  The  isolation  of  argon,  the  first  of  the  series 
to  be  recognized  and  also  the  most  abundantly  occurring  mem- 
ber, was  due  in  the  first  instance  to  physical  research,  Lord 
Rayleigh  (1893),  who  was  engaged  in  checking  the  densities  of 
the  principal  gases,  observing  that  nitrogen  from  the  atmosphere 
was  always  slightly  heavier  than  that  prepared  from  chemical 
compounds.  He  and  Ramsay  found  this  was  not  due  to  any 
peculiarity  of  the  nitrogen  present  in  either  case,  and  therefore 
set  out  to  repeat  Cavendish's  work  on  the  question  of  the 
homogeneity  of  nitrogen — only  with  all  the  advantages  of 
modern  appliances  and  methods.  The  meaning  of  the  last 
sentence  may  be  realized  when  it  is  reflected  that  these  later 
investigators  had  at  their  command  (a)  spectrum  analysis,  where- 
by traces  of  any  gas  could  be  qualitatively  determined  with  the 
greatest  ease  (cf.  chap,  x.,  p.  186) ;  (ti)  methods  for  cooling  air 
sufficiently  to  liquefy  it,  whereby  huge  volumes  of  gas  could  be 
treated  at  once  (cf.  chap,  x.,  p.  174);  (c)  chemical  means  of 
absorbing  nitrogen  and  other  gases  which  were  unknown  in 
Cavendish's  time.  They  found,  by  repeating  Cavendish's  ex- 
periment of  sparking  the  residual  gas  with  oxygen  over  potash, 
and  also  by  passing  nitrogen  repeatedly  over  heated  magnesium 
or  calcium,  that  a  residue  of  inert  gas,  giving  an  altogether  new 
spectrum,  was  left.  This  they  termed  argon,  from  its  incapability 
of  entering  into  chemical  reactions. 

It  was  known  that  a  gas,  supposed  to  be  nitrogen,  was  often 
found  occluded  in  uranium  minerals  (cleveite,  brb'ggerite, 
pitch-blende,  etc.).  These  were  next  examined  by  Ramsay  and 
from  them  in  1895  he  obtained  another  inactive  gas  much  lighter 
than  argon,  previously  only  observed  in  the  sun  (by  Sir  N, 


22  A  SHORT  HISTORY  OF  CHEMISTRY 

Lockyer,  who  christened  it  helium,  in  1868),  and  at  once  re- 
cognized by  its  spectrum  (with  a  notable  yellow  line — "  D3 "). 
Argon  was  also  sometimes  obtained,  one  mineral — malacone — 
giving  this  as  the  chief  occluded  gas.  The  residue  from  air 
termed  "argon  "  was  therefore  prepared  in  large  amount  in  1898 
by  Ramsay  and  Travers  and  fractionally  distilled  at  very  low 
temperatures ;  two  main  fractions  were  obtained,  and  of  these, 
the  lower  boiling  one  gave  by  repeated  distillation  two  gases, 
helium  and  another  new  member,  neon,  while  the  other  consisted 
mainly  of  pure  argon  with  two  heavier  gases,  krypton  and  xe?ion. 
There  was  thus  obtained  a  series  of  five  new  gases  of  unprece- 
dented nature,  in  that  they  seemed  to  be  devoid  of  all  chemical 
affinity,  no  compound  of  any  of  them  being  known.  Their 
physical  constants  have  been  determined  fairly  fully  and  are 
given  in  the  table  below  ;  the  atomic  weights  are  determined  from 
the  densities,  for  Ramsay  found  by  the  method  of  Kundt  and 
Warburg  (cf.  p.  189),  that  the  ratio  of  specific  heat  at  constant 
pressure  to  that  at  constant  volume  was  about  i'6o  in  all 
cases,  the  gases  being  accordingly  monatomic.  The  spectra, 
boiling-points,  melting-points,  etc.,  have  also  been  determined  by 
various  workers,  notably  Ramsay,  Travers,  and  Dewar ;  helium 
was  not  liquefied  for  some  time,  but  Kamerlingh  Onnes  finally 
succeeded  in  condensing  it  by  the  Linde-Hampson  process 
(p.  174),  in  1908.  Careful  search  has  been  made  by  Moore 
in  Ramsay's  laboratory  for  members  of  the  series  heavier  than 
xenon,  but  without  success  (1908).  The  table  shows,  as  well  as 
the  physical  properties,  the  approximate  amounts  of  each  pre- 
sent in  air,  from  which  it  will  be  seen  that  the  designation  "  rare 
gases  of  the  atmosphere  "  is  not  very  apt,  since  together  they 
comprise  almost  one  per  cent  thereof,  besides  occurring  oc- 
cluded in  various  minerals,  and  dissolved  in  many  springs,  etc. 
Their  relation  to  the  problem  of  radio-activity  is  not  yet  com- 
pletely understood,  but  it  may  be  said  here  that  Ramsay  has 
proved  that  helium  at  least  is  one  of  the  disintegration  products 
of  radium,  and  that  "  radium  emanation  "  is  a  gas  possessing 
the  properties  of  a  higher  mernber^of  the  series, 


THE  CHEMICAL  HISTORY  OF  WATER         23 


Percentage  in  Atomic  Weight    Boiling- 

Melting- 

Name. 

Atmosphere. 

(1910). 

point 

point. 

(760  m.). 

Helium 

0-0005 

4-0 

4-5°  abs. 

Below  3°  abs. 

Neon 

0-0025 

20-O 

-  243°  C. 

-253°C. 

Argon 

0-942 

39'9 

-  i86-i°C. 

-  189-6°  C. 

Krypton 

O-OOO02 

83-0 

-  1517 

-  169-0 

Xenon 

Less  than  any 

1307 

-  109-1 

-  140*0 

of  the  above 

§  5.  Water — The  story  of  water  is  a  much  simpler  one 
than  those  of  either  air  or  fire.  From  the  earliest  times  right 
down  to  the  end  of  the  phlogistic  period  (and,  in  isolated  in- 
stances, even  later)  it  was  looked  upon  as  an  "  element  ".  The 
ancients  seem  to  have  thought  that  water  and  air  could  be 
transformed  into  each  other,  and  also  that  water  was  readily 
converted  into  "  earth  " — another  proof  that  "  element  "  did  not 
then  mean  a  definite  unitary  species  of  matter.  The  latter  idea 
crops  up  persistently  through  the  next  two  periods  :  thus  Basil 
Valentine,  who  realized  the  importance  of  water  to  plant  and 
animal  life,  held  that  it  was  transformed  in  the  organic  economy 
into  earthy  matters,  and  amongst  the  phlogistonists  we  find 
Scheele  engaged  in  a  qualitative  analysis  of  the  solids  left  by 
evaporation  of  water  (he  mentions  lime  and  silica  as  the  chief), 
while  Lavoisier's  first  purely  chemical  service  was  to  show  that 
such  solids  were  either  primarily  dissolved  in  the  water,  or 
dissolved  by  it  out  of  the  containing  vessels. 

We  owe  the  discovery  of  the  compound  nature  and  quali- 
tative composition  of  this  all-important  liquid,  however,  to 
Cavendish,  who  proved  definitely  that  when  hydrogen  burns, 
water  is  the  sole  product  of  combustion.  And  here  we  may 
conveniently  recount  the  history  of  hydrogen.  The  gas  and  its 
formation  from  iron  and  dilute  acids  were  known  to  van 
Helmont,  who  seemed  to  confound  it  with  carbonic  acid.  Its 
Inflammability  had  been  observed  by  others  of  the  later  al- 
chemists and  by  Boyle ;  its  reducing  properties  caused  not  a  few 
of  the  phlogistic  chemists  to  look  upon  it  as  phlogiston  itself. 
The  liquid  formed  when  it  burned  was  usually  believed  to  bg 


24  A  SHORT  HISTORY  OF  CHEMISTRY 

an  acid  until,  as  just  mentioned,  Cavendish  (about  1782)  showed 
this  to  be  pure  water.  He  proved  that  hydrogen  (or  inflam- 
mable air,  .to  use  his,  phlogistic  term)  was  only  explosive  in 
presence  of  air  or  oxygen,  thereby  pointing  out  the  remaining 
constituent  of  water,  and  he  determined  the  relative  weight  of 
the  gas  with  moderate  accuracy.  Although  Cavendish  used 
hydrogen  in  determining  the  composition  of  air,  it  was  Lavoisier 
who,  in  1783,  made  the  first  quantitative  synthesis  of  water. 
Lavoisier  (1787)  also  gave  hydrogen  its  modern  name  ("water- 
producer  "),  and  showed  how  this  gas  could  be  formed  by  the 
action  of  steam  on  red-hot  iron.  The  direct  quantitative 
analysis  of  water  came  a  little  later,  when  Nicholson  and 
Carlisle  succeeded  in  decomposing  it  by  electrolysis  (1800). 
The  true  composition  of  water,  then,  became  known  at  about 
the  beginning  of  the  nineteenth  century,  but  the  notion  of  its 
elementary  nature  died  very  hard,  even  Priestley  remaining 
unconvinced  for  some  years. 

§  6.  Fire :  Lavoisier's  Revolution — In  following  up  the 
history  of  air  and  water  we  have  been  forced  to  make  a  digres- 
sion from  that  of  combustion,  which  it  will  be  recalled  had 
been  traced  down  to  the  time  at  which  the  phlogistic  theory 
held  full  sway.  We  must  now  return  in  point  of  time  to  the 
years  immediately  preceding  and  following  the  French  Revolu- 
tion (1791) — as  crucial  a  period  for  modern  chemistry  as  for 
modern  politics,  though  for  vastly  different  reasons. 

Somewhat  previous  to  the  year  1770  the  French  scientist 
Lavoisier  was  attracted  by  the  twin  phenomena  of  combustion 
and  calcination,  owing,  in  the  first  instance,  to  a  request  to 
investigate  means  for  lighting  the  streets  of  Paris.  As  a  physi- 
cist (and  physics  at  that  time  meant  mainly  astronomy,  optics 
and  mathematics — all  three  sciences  requiring  precision  of 
measurement)  it  was  natural  that  he  should  have  paid  much 
more  than  usual  attention  to  the  quantity  of  the  substances  re- 
acting, and  that  to  this  end  he  should  have  provided  himself 
with  a  delicate  balance.  In  1772,  in  a  private  communication 


THE  CHEMICAL  HISTORY  OF  WATER         25 

to  the  French  Academic  des  Sciences,  he  reported  that  metals, 
phosphorus  and  sulphur  gain  in  weight  and  absorb  "  air  "  when 
heated  in  the  atmosphere,  while  by  heating  a  metal  oxide 
(litharge)  with  coal  much  "  air "  was  generated,  as  well  as 
the  reduced  metal.  This  report  betrays  a  tendency  to  go  to 
the  opposite  extreme  of  the  usual  failing,  or,  in  other  words, 
to  neglect  the  qualitative  side  of  chemical  reactions,  for  he 
failed  almost  entirely  to  distinguish  between  the  different  kinds 
of  "air".  Let  it  be  remarked,  too,  that  increase  in  weight  on 
calcination  had  been  observed  by  Rey  and  Mayow  more  than 
a  century  previous  to  this,  the  latter  being  apparently  well  on 
the  way  to  the  correct  explanation  of  the  process  when,  at  a 
somewhat  early  age,  he  died. 

Lavoisier,  however,  repeated  the  work  of  1772  and  produced 
a  series  of  results  which  settled  once  and  for  all  the  problems 
of  combustion,  calcination,  and  respiration.  These  must  be 
briefly  summarized. 

In  1774  he  heated  tin  in  a  closed  vessel  and  found  the 
weight  to  be  exactly  the  same  before  and  after  the  process ; 
but  on  opening  the  vessel  air  entered  into  it  in  an  amount 
which  showed  that  the  deficit  of  air  in  the  vessel  was  equal  to 
an  increase  in  weight  which  the  tin  itself  was  found  to  have 
undergone.  During  the  same  year  Priestley  told  him  of  the 
isolation  of  " dephlogisticated  air".  Lavoisier  then  repeated 
the  tin  experiment  with  mercury,  and  from  the  oxide  formed  he 
reproduced  the  new  gas  according  to  Priestley's  method ;  in 
this  way  he  realized  that  the  essential  part  in  these  processes 
was  .played  by  "dephlogisticated  air  " — it  is  unfortunate  to  have 
to  say  that  he  avoids  any  mention  of  either  Priestley  or  Scheele's 
work  on  the  discovery  of  that  gas !  The  next  two  years  were 
occupied  by  proving  that  the  combustion  product  of  diamond 
and  of  wood  charcoal  was  "  fixed  air,"  and  that  many  "  organic  " 
bodies  (alcohol,  oils,  fats,  etc.)  gave  only  fixed  air  and  water  by 
their  combustion ;  this,  of  course,  showed  such  bodies  to  be 
made  up  only  of  carbon,  hydrogen  (and  perhaps  oxygen),  but 


26  A  SHORT  HISTORY  OF  CHEMISTRY 

the  composition  of  water  not  being  then  known,  this  deduction 
was  not  made  for  some  few  years.  In  1777  he  showed  that 
phosphorus  leaves  four-fifths  of  the  volume  of  enclosed  air  in 
which  it  burns  untouched,  but  completely  consumes  similarly 
enclosed  dephlogisticated  air ;  that  sulphuric  acid  consists  of 
sulphurous  acid  (known  to  be  formed  when  sulphur  burns  in 
air)  and  dephlogisticated  air,  by  prolonged  heating  of  quick- 
silver with  sulphuric  acid,  when  first  the  former  and  then  the 
latter  gas  is  evolved  (this  experiment,  in  separate  parts,  had 
been  made  previously  by  Priestley) ;  and  that  nitric  acid  is 
similarly  constituted  (the  more  detailed  investigation  of  the 
composition  of  nitric  acid  is  due  to  Cavendish).  With  all  these 
facts,  he  was  in  a  position  to  enunciate  his  "oxidation  theory"  : 
Substances  burn  only  in  "pure  air"  which  is  used  up  in  the  pro- 
cess^ the  weight  of  air  used  balancing  the  gain  in  weight  of  tJie 
substance.  Tfie  product  of  combustion  is  usually  an  acid,  but 
metals  give  the  metallic  calces.  A  little  later,  concluding  that 
his  "  pure  air  "  was  a  constituent  of  all  acids,  he  suggested  its 
modern  name,  oxygen  (1781).  This  later  work  consisted  in 
investigating  the  combinations  of  metals  with  oxygen  and  the 
nature  of  the  different  "  calces  ".  The  only  difficulty  in  the 
way  of  his  theory  was  that  no  explanation  was  given  of  the 
reasons  for  the  dissolution  of  metals  in  acids  and  the  evolution 
of  hydrogen  at  the  same  time.  Cavendish's  synthesis  of  water 
(1783)  gave  the  clue  to  this,  and  so  it  may  be  said  that  by 
about  1785  Lavoisier's  "  oxidation  theory  "  was  complete,  and 
in  the  course  of  the  next  two  decades  completely  supplanted 
the  topsy-turvy  explanation  furnished  by  the  phlogistonists. 


CHAPTER  III 
THE  ULTIMATE  CONSTITUTION  OF  MATTER 

§  i.  Ancient  and  Alchemical  Yiews — In  the  sixth  cen- 
tury B.C.  Thales,  Anaximenes  and  Heraclitus  assumed  for 
varying  reasons  that  water,  air,  or  fire  respectively  was  the 
primary  material  out  of  which  the  universe  was  evolved.  Such 
views  were  not  of  great  individual  influence,  but  Empedocles, 
about  440  B.C.,  gave  utterance  to  the  idea  of  four  fundamental 
elements — earth,  air,  fire,  and  water — a  view  possibly  derived  in 
some  degree  from  dimly-known  Hindu  and  Chinese  systems 
of  thought.  Some  hundred  years  later  Aristotle  modified  this 
theory  by  teaching  that  "  matter  "  was  the  outward  result  of  the 
combination  of  "  properties  " ;  there  were  four  essential  "  pro- 
perties"— heat,  cold,  damp,  dryness — besides  a  number  of 
secondary  ones,  all  carried  about  by  one  original  matter. 
Combinations  of  these  properties,  two  by  two,  were  the 
"elements"  from  which  all  matter  was  made;  thus: — 

Properties.        Element.  Properties.  Element. 

Heat  +  damp  AIR  Cold  +  damp  WATER 

Heat  +  dryness        FIRE  Cold  +  dryness        EARTH 

He  further  declared  that  another  element  of  an  immaterial 
or  ethereal  nature  was  necessary  for  a  complete  explanation  of 
natural  phenomena  (this  ethereal  constituent  was  later  called 
the  "  quinta  essentia,"  and  long  after  this  was  sought  by  the 
alchemists  as  the  "  purest "  form  of  matter,  and  identified  by 
them  with  their  imaginary  elixir).  Aristotle's  somewhat  fanci- 
ful doctrine  is  noteworthy,  because  by  the  mutation  of  his 

27 


28  A  SHORT  HISTORY  OF  CHEMISTRY 

"properties"  the  observed  transformations  of  natural  bodies 
could  be  explained. 

Somewhat  earlier  (about  425  B.C.)  Democritus  had  suggested 
that  by  repeated  subdivision  of  matter  a  point  would  be 
reached  when  no  further  subdivision  was  possible.  The  body 
thus  isolated — a  "  first  beginning,"  or  atom  of  matter — was  the 
ground  material  of  the  universe,  and,  according  to  our  philo- 
sopher, all  such  atoms  were  of  the  same  nature  and  in  continual 
motion,  but  differed  in  form  and  size. 

These  two  doctrines  were  co-ordinated  and  developed  by 
succeeding  philosophers,  notably  by  Epicurus  (345-274  E.G.), 
and  an  elaborate  account  of  the  latest  phase  of  ancient  theory 
is  given  by  the  Latin  poet  Lucretius  in  his  work,  "  De  Rerum 
Natura,"  published  about  58  B.C.  "The  void,  or  aether,  per- 
vades everywhere,  while  the  matter  is  made  up  of  a  certain 
primal  element  and  its  aggregates.  This  element  exists  in  the 
form  of  infinitely  small,  ever-vibrating  first-beginnings  or  atoms, 
of  finite  shape,  but  giving  rise  by  varied  combinations  to  bodies 
of  infinite  shape,  either  solid  (when  the  atoms  are  tightly  packed) 
or  liquid  or  gas,  air  or  light  (when  they  are  not  in  such  dense 
aggregates)." 

The  term  element  possessed  an  indefinite  meaning  in  the 
next  period,  and  sometimes  referred  to  the  actual  matter  in  a 
substance,  sometimes  to  a  property  of  that  matter,  but  never  to 
a  simple  substance!  In  general,  the  alchemical  "element" 
meant  something  more  related  to  properties  than  to  matter 
itself — something  which  we  can  perhaps  best  depict  by  the 
word  "principle".  Thus  Geber  (eighth  century)  states  (it  is 
not  clear  upon  what  grounds)  that  all  metals  contain  two  such 
principles — sulphur  and  mercury,  the  latter  imparting  metallic 
properties,  such  as  glance,  ductility,  etc.,  and  the  former  readiness 
of  decomposition,  the  different  properties  of  metals  depending 
on  the  varying  amounts  of  these  two  principles,  which,  however, 
must  not  be  confounded  with  the  actual  chemical  substances  of 
the  same  name,  Quicksilver  and  sulphur,  in  the  usual  sense, 


THE  ULTIMATE  CONSTITUTION   OF  MATTER     29 

were  assumed  to  be  bodies  containing  maximum  amounts  of 
the  respective  principles.  Other  Arabian  authors  held  much 
the  same  view,  but  amongst  the  Christian  nations  the  influence 
of  the  Aristotelian  doctrine  and  of  a  mystical  importance 
attached  to  the  number  three  is  noticeable.  The  third  "  prin- 
ciple," first  assumed  by  Basil  Valentine  (fifteenth  century),  was 
"  salt,"  the  principle  of  resistance  to  fire.  Some  alchemists  used 
different  names  for  the  principles ;  thus  Albertus  Magnus  calls 
them  water,  arsenic,  and  sulphur,  and  so  it  is  hard  to  make  any 
serious  generalization  on  the  subject.  The  iatro-chemists  natur- 
ally paid  less  attention  to  the  ultimate  composition  of  substances, 
and  this  perhaps  led  to  the  loosely  defined  way  in  which  the 
three  principles  are  referred  to  by  many  of  the  later  alchemists  ; 
these  were,  however,  always  tacitly  assumed,  and  Paracelsus 
(sixteenth  century)  asserts  that  organized  as  well  as  inert 
nature  consists  essentially  of  varying  combinations  of  "  sulphur, 
salt,  and  mercury".  Finally  Becher  (seventeenth  century)  gave 
these  alchemical  elements  a  new  series  of  names,  as  appears  in 
the  following  summary  : — 

ALCHEMICAL  PRINCIPLES. 

Of  Solidification 

Of  Metallicity  Of  Changeability        or  Resistance 
or  Durability.         or  Dross.  to  Fire. 

Geber         .         .  Quicksilver  Sulphur 

Basil  Valentine  .  „  „  Salt 

Parace,-.        -      {$&££} 

Becher        .        .      Mercurial  earth  Combustible  earth    Vitreous  earth 

The  lax  nomenclature  as  well  as  the  duplicity  of  not  a  few 
alchemists  was  scathingly  criticized  towards  the  close  of  the 
seventeenth  century  by  Kunkel  and  by  Boyle,  who  was  the  first 
chemist  to  say  precisely  what  he  meant  by  "  element,"  giving  at 
the  same  time  a  definition  which  has  lasted :  a  substance 
which  has  not  yet  been  decomposed  into  simpler  ones  ("  Chemista 
Scepticus,"  1661).  While  suggesting  that  the  then  so-called 
elements  were  not  necessarily  simple,  he  yet  predicted  a  much 


30  A  SHORT  HISTORY  OF  CHEMISTRY 

larger  number  of  real  elements  than  the  Aristotelian  four  or 
the  alchemistic  three,  although  he  doubted  if  the  elements  so 
obtainable  by  chemists  would  represent  the  absolutely  ultimate 
origin  of  matter. 

§  2.  The  Evolution  of  Chemical  Nomenclature — No 
further  contribution  of  any  permanent  value  to  the  problem 
took  place  for  a  century  after  Boyle's  time,  for,  naturally,  so 
long  as  people  were  in  error  with  reference  to  the  supposed 
phlogiston  there  was  an  inversion  of  opinion  as  to  whether 
"  calx  "  or  "  metal  "  was  the  real  element.  As  soon  as  Lavoi- 
sier's theory  of  combustion  was  definitely  accepted  the  way  was 
open  for  a  sweeping  generalization  of  the  host  of  chemical  sub- 
stances then  known.  Lavoisier  himself  undertook  the  task 
(1787),  adopting  as  the  basis  of  his  system  Boyle's  definition  of 
an  element.  With  a  few  modifications  he  used  the  nomen- 
clature introduced  a  little  earlier  (i  782)  by  Guyton  de  Morveau, 
one  of  the  founders  of  and  professor  of  chemistry  in  the  "  Ecole 
polytechnique  "  at  Paris.  This  was  as  follows  : — 

CHEMICAL  SUBSTANCES. 


Elements.  Compounds. 

(Five  classes.)  (Two  classes.) 

(i)  Heat, light,  oxygen,  nitrogen,  hydrogen.         (i)  Binary  (acids,  bases), 
(ii)  Acid-forming   elements   (sulphur,   car- 
bon, etc.).  (ii)  Ternary  (salts), 
(iii)  Metals    (we     should     say     "heavy" 

metals,  iron,  copper,  etc.). 
(iv)  Earths  (lime,  magnesia,  alumina,  etc.). 
(v)  Alkalies    (only    decomposed    by    Davy 

years  later). 

Acids  and  bases,  being  regarded  at  that  time  as  combinations  of  an 
element  with  oxygen,  were  termed  binary  compounds. 

Lavoisier's  chief  alteration  had  reference  to  the  last  two 
classes  of  "  elements,"  of  the  simple  nature  of  which  he  was 
doubtful ;  indeed,  two  years  later  he  felt  the  necessity  of  elimi- 
nating the  alkalies  entirely  from  the  list  of  elements.  We  may 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     31 

as  well  complete  the  story  of  chemical  nomenclature  at  this 
point ;  as  we  shall  shortly  see,  the  discovery  of  the  fundamental 
rules  of  chemical  combination  and  the  doctrine  of  ' '  atoms  "  in 
its  modern  form  soon  followed  the  adoption  of  Lavoisier's  views. 
These  in  turn  led  to  the  investigation  and  accurate  analysis  of 
a  great  many  inorganic  materials,  and  in  this  field  no  more 
active  and  skilful  worker  existed  than  the  great  Swedish  chemist 
Berzelius.  His  enlightened  views  and  abundant  experience  fitted 
him  for  the  work  of  extending  and  adapting  Lavoisier's  nomen- 
clature to  include  the  additional  facts  known  by  1811.  In  that 
year  he  published  his  first  system  of  nomenclature,  based  upon 
his  electro-chemical  or  "  dualistic  "  theory  of  chemical  union 
(see  chap,  iv.,  p.  50)  : — 

CHEMICAL  SUBSTANCES. 


Elements.  Compounds. 

Electro-positive.     Electro-negative.     Electro-positive.     Electro-negative. 
Metals.  Metalloids  Basic  oxides.  Acid  oxides. 

("  non-metals  ").  v » ' 

Salts. 

He  tried  to  extend  the  dualistic  system  and  its  nomenclature 
to  organic  compounds,  but  met  with  little  success  in  that  direc- 
tion. He  also  invented  a  simple  method  of  chemical  "  short- 
hand," or  abbreviation,  which  is  practically  that  now  in  use,  and 
so  need  not  be  detailed  here.  A  certain  amount  of  confusion 
resulted  from  the  fact  that  Berzelius  referred  all  his  formulae  to 
the  "  oxygen  "  standard,  or,  in  other  words,  took  a  bivalent  ele- 
ment as  unit  of  combination,  and,  further,  was  not  definite  with 
reference  to  the  distinction  between  equivalent  and  atomic 
weight.  This  led  him  to  the  use  of  "  barred  "  symbols  to  repre- 
sent what  he  called  "  double  atoms  "  in  the  case  of  compounds 
containing  two  monovalent  atoms  combined  with  oxygen  ;  thus 
he  wrote  HO  and  not  H2O,  and  so  on.  This  ambiguity  may  be 
the  reason  why  his  notation,  now  universally  adopted,  was  at 
first  received  with  a  good  deal  of  coolness,  and,  indeed,  open 


32  A  SHORT  HISTORY  OF  CHEMISTRY 

opposition,  especially  in  conservative  England.  The  only  other 
modern  notation  emanated  from  Dalton,  who  assigned  to  the 
more  common  elements  various  geometrical  symbols,  and  repre- 
sented their  combinations  by  placing  the  appropriate  symbols  in 
juxtaposition.  This  method  was  naturally  far  too  cumbrous  to 
be  permanent,  though  doubtless  it  was  of  value  in  the  early 
struggles  of  the  atomic  theory,  giving,  as  it  must  have  done,  a 
mental  picture  of  the  way  in  which  the  atoms  united  to  form 
compound  bodies. 

§  3.  Discovery  of  Equivalent  Combining  Proportions 
— Given  Boyle's  definition  of  an  element  and  Lavoisier's  proof 
of  what  substances  were  elementary  and  what  were  compound, 
it  is  possible  without  reference  to  any  further  hypothesis  to 
divide  chemical  substances  into  the  different  classes  enumerated 
by  Berzelius.  This  does  not  apply,  of  course,  to  the  Berzelian 
notation,  which,  as  far  as  its  quantitative  significance  is  con- 
cerned, is  based  upon  the  atomic  hypothesis.  It  only  remains 
now  to  discuss  this  important  subject  and  its  later  development, 
for  all  modern  work  connected  with  Dalton's  theory  has  so  far 
served  to  amplify  and  not  to  contradict  it. 

The  establishment  of  the  theory  is  really  due  to  both  English 
and  Continental  workers.  No  one  has  ever  questioned  that 
the  genius  and  perception  of  Dalton  led  to  his  enunciation  of 
the  doctrine  of  atoms  ;  it  was  his  idea,  and  was  confirmed  by 
his  own  experimental  work.  Nevertheless,  when  his  views 
were  published,  it  was  seen  that  other  and  somewhat  earlier 
work  afforded  strong  confirmatory  evidence  in  support  thereof. 

For  instance,  J.  B.  Richter  (1791-1800)  showed  that  mixed 
solutions  of  two  neutral  salts  invariably  remained  neutral, 
whether  double  decomposition  took  place  or  not ;  he  concluded 
that  the  two  quantities  x  and  y  of  two  different  bases  X  and 
Y  which  neutralized  the  same  amount  a  of  an  acid  A  would 
each  neutralize  an  amount  b  of  another  acid  B,  and  conversely. 
He  also  measured  the  different  amounts  of  metals  precipitated 
from  salt  solutions  by  certain  other  metals,  and  gave  to  the 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     33 

'  whole  process  the  name  Stoichiometry — the  measurement  of 
the  proportion  by  weight  in  which  substances  combine. 

Again,  in  1808,  shortly  after  Dalton  had  published  his  theory, 
Gay-Lussac  published  results  on  the  volume  relations  of  re- 
acting gases,  showing  that  the  volumes  entering  into  combina- 
tion bore  to  each  other  and  to  the  products  (if  gaseous)  a 
simple  numerical  ratio.  Thus  he  proved  that 

2  volumes  of  carbon  monoxide  and  I  volume  of  oxygen  give  2  volumes 

of  carbonic  acid. 
I  volume  of.  nitrogen  and  3  volumes  of  hydrogen  give  2  volumes  of 

ammonia. 

He  readily  perceived  in  this  a  confirmation  of  Dalton's  view, 
while,  curiously  enough,  the  latter  worker,  as  we  shall  shortly 
see,  was  inclined  to  regard  it  as  a  stumbling-block. 

§4.  Dalton's  Atomic  Theory — How,  then,  was  Dalton 
led  to  the  conception  of  his  "  atoms  "  ?  It  came  about  entirely 
independently  of  all  this  previous  work,  and,  in  a  more  distinc- 
tive way  than  many  other  famous  advances  in  science  connected 
with  different  names,  was  due  to  the  man's  own  work  and 
thought.  He  had  been  analysing  olefiant  gas  (ethylene)  and 
light  carburetted  hydrogen  (methane)  and  found  that,  for  a 
given  amount  of  carbon,  the  latter  contained  exactly  twice  as 
much  hydrogen  as  the  former.  Struck  by  the  simple  relation 
thus  disclosed  he  proceeded  to  analyse  carbonic  oxide  and 
carbonic  acid  gas,  of  course  with  precisely  similar  results.  In 
this  way  the  Law  of  Multiple  Combining  Proportions  was  dis- 
covered, and  its  truth  was  emphasised  still  further  when  he 
investigated  the  series  of  four  nitrogen  oxides  and  acids  then 
known. 

What  did  this  simple  numerical  rule  imply?  Some  earlier 
researches  by  Dalton  helped  him  towards  an  answer.  In  some 
work  on  the  solubility  of  gases  in  water  he  had,  like  his  con- 
temporary and  colleague,  Henry,  noted  how  pressure  increases 
the  capacity  of  a  gas  to  dissolve.  It  seemed  as  if  the  water 
was  a  mass  of  minute  particles  between  which  the  gas  particles, 
3 


34  A  SHORT  HISTORY  OF  CHEMISTRY 

which  would  be  "  rarer  "  and  more  volatile,  could  move  to  a 
certain  extent,  and  then  by  increased  pressure  more  of  the 
gas  particles  would  be  forced  into  the  interstices  of  the  water- 
particles.  Thus  supplied  with  the  rudimentary  idea  of  an 
atom,  it  was  easy  to  extend  it.  If  the  gases  were  an  assemblage 
of  such  particles,  in  any  one  gas  all  the  particles  must  be  alike, 
and  moreover  any  action  in  which  the  gas  participated  must  be 
made  up  of  the  actions  of  the  several  particles.  In  other 
words,  when  two  gases  joined  to  form  a  third,  the  process  was 
the  result  of  the  union  of  their  constituent  particles.  It  was 
obvious,  too,  that  one  particle  of  a  substance  might  be  joined 
to  one,  or  to  two,  or  to  some  other  definite  number  of  particles 
of  another  substance — thus  explaining  the  rule  of  multiple  pro- 
portions. So  in  1807-8,  the  Atomic  Theory  was  enunciated 
as  follows  in  Dalton's  "  New  System  of  Chemical  Philosophy  "  : — 

(1)  Every  element  consists  of  homogeneous  atoms  of  constant 
weight. 

(2)  Chemical  compounds  are  formed  by  the  union  of  different 
elementary  atoms  in  the  simplest  numerical  proportions. 

Dalton  naturally  proceeded  to  the  determination  of  the  re- 
lative atomic  weights  of  the  elements,  assuming  that  these 
combined  in  the  simplest  possible  atomic  proportions,  and 
taking  hydrogen  as  the  unit  of  his  system.  These  results, 
which  were  not  very  accurate,  expressed  therefore  the  equivalent 
combining  weight,  and  not  the  atomic  weight  (in  the  modern 
sense  of  the  term). 

Dalton's  theory  differs  from  the  old  Greek  views  of  atoms 
and  from  Boyle's  "corpuscles,"  which  were  the  ultimate  par- 
ticles of  matter  and  by  mutual  attraction  and  repulsion  pro- 
duced chemical  combination  and  decomposition,  in  that  it 
demands  that  the  atoms  of  each  element  are  entirely  distinct 
species  of  matter,  and,  as  first  enunciated,  places  a  bar  against 
the  notion  of  an  ultimate  primary  material.  He  succeeded  in 
showing : — 

(a)  How  the  elements  may  be  made  up  of  atoms  ; 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     35 

(b)  How  these  atoms  may  unite  to  form  compounds ; 

(c]  How  to  determine  the  relative  combining  weights  of  the 
atoms. 

§  5.   Development   of  the   Atomic    Hypothesis — The 

conception  of  atoms  was  at  once  accepted  by  the  leading 
chemists,  but  most  of  these  (e.g.  Davy,  Gay-Lussac,  Wollas- 
ton)  perceived  that  the  actual  relative  weights  determined 
according  to  Dalton's  principles  were  merely  the  combining 
weights,  and  that  no  light  was  thereby  thrown  on  the  relative 
weights  of  the  atoms  themselves.  There  was  also  the  other 
difficulty  arising  out  of  Gay-Lussac's  "  Law  of  Volumes  " ;  ac- 
cording to  his  work  on  this  subject,  for  instance,  one  volume 
of  nitrogen  and  one  volume  of  oxygen  gave  two  volumes  of 
nitric  oxide,  whilst  obviously  one  atom  of  nitrogen  and  one 
atom  of  oxygen  would  give  only  one  "atom"  of  nitric  oxide. 
The  difficulty  of  an  "  atom  "  of  nitric  oxide  occupying  twice 
the  volume  of  the  atom  of  either  element  was  cleared  up  by 
the  Italian  chemist  Avogadro  in  1811.  He  assumed  that : — 

(a)  Under   equal  conditions  of  temperature  and  pressure, 
equal  volumes  of  all  gases  contained  equal  mimbers  of  molecules  ; 

(b)  There   were    two    sorts    of  ultimate    particles,    "  mole- 
cules integrantes  "  (molecules)  and  "  molecules  elementaires  " 
(atoms) ; 

(c)  The  ultimate  particles  of  an  element  might  be  molecules 
composed  of  more  than  one  atom. 

Returning  to  the  previous  point,  viz.  the  difference  between 
equivalent  weight  and  atomic  weight,  we  might  fill  a  chapter 
with  a  description  of  the  uncertainty  and  confusion  which  pre- 
vailed in  the  first  half  of  last  century  with  respect  to  these  two 
terms.  Some,  like  Davy  or  Gay-Lussac,  held  that  the  deter- 
mination of  the  relative  weights  of  atoms  themselves  was  impos- 
sible ;  others,  and  of  these  Berzelius  was  foremost,  adopted  the 
opposite  conclusion.  Berzelius  himself  attacked  the  problem 
with  amazing  thoroughness,  and  in  the  course  of  ten  years  had 
made  fairly  reliable  analyses  of  compounds  of  practically  all  the 


36  A  SHORT  HISTORY  OF  CHEMISTRY 

known  elements.     From  the  equivalents  so  obtained  he  chose 
his  atomic  weights  on  the  following  system  : — 

(a)  With  elements  possessing  volatile  compounds  he   made 
use  of  Gay-Lussac's  and  Avogadro's  volume-relations. 

Thus,  starting  from  2  volumes  of  hydrogen  and  i  of  oxygen  giving  2 
of  water,  he  saw  that  in  water  2  atoms  of  hydrogen  were  united  to  i  of 
oxygen,  and  so  obtained  the  true  atomic  weight  of  oxygen. 

(b)  With  other  elements  he  worked  on  the  ratio  of  metal  to 
oxygen,  and  assumed  that  in  general  only  i  atom  of  the  metal 
was  present  per  molecule. 

In  this  way  he  came  to  regard  proportions  such  as  2  :  3  or  2  :  5  as  too 
complex,  and  therefore  formulated  the  iron  oxides,  for  instance,  as  FeO2 
and  FeO3,  and  not  FeO  and  Fe2O,  as  at  present ;  so  that  what  we  now 
know  to  be  dyad  metals  received  double,  and  monad  metals  received 
quadruple  their  present  atomic  weights. 

(c)  He  always  took  oxygen  for  the  basis  of  his  calculations, 
and  indeed,  in  his  tabulated  results,  took    100  as  the  atomic 
weight  of  oxygen.     (Later  on  it  was  thought  better  to  refer  all 
atomic  weights  to  H  =  i  as  the  standard,  since  hydrogen  was 
the  lightest  element.     In  this  way  the  atomic  weight  of  oxygen 
becomes  15*88,  and,  since  the  majority  of  atomic  weight  deter- 
minations involve  the  ratio  element :  oxygen,  it  has  latterly  be- 
come the  custom  to  call  the  atomic  weight  of  the  latter  1 6-00,  and 
refer  hydrogen  (1-008)  and  all  the  other  elements  to  this  value.) 

This  first  atomic  weight  table  of  Berzelius  was  complete  about 
1817.  We  can  only  briefly  summarize  its  subsequent  career. 

In  1819  Mitscherlich  brought  out  his  "  Law  of  Isomorphism," 
stating  that  the  amounts  of  elements  which  replaced  each  other 
in  isomorphous  compounds  were  chemically  equivalent  and 
represented  the  relative  weights  of  the  replacing  atoms,  and 
about  1821  Dulong  and  Petit  showed  that  in  many  cases  the 
product  of  specific  heat  and  atomic  weight  was  a  constant 
number. 

Both  these  rules  were  of  assistance  to  Berzelius,  though  he 
attached  but  a  minor  importance  to  the  second. 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     37 

His  second  atomic  weight  table  (1826)  was  rendered  neces- 
sary because  he  found  reasons  for  halving  many  of  the  values 
he  had  previously  selected. 

Analyses  of  the  chromates  showed  that  chromium  trioxide  was  repre- 
sented by  CrO3,  so  that  the  basic  oxide  must  be  Cr2O3.  Hence  ferric 
oxide  was  Fe2O3  and  the  "  protoxide "  FeO,  and  by  isomorphism  he 
deduced  similar  atomic  weights  for  the  allied  metals. 

Next  year,  however,  doubt  was  cast  on  his  fundamental 
assumption  that  the  weights  of  equal  gaseous  volumes  of  the 
elements  were  proportional  to  the  atomic  weights  by  the 
French  chemist  Dumas,  who,  by  his  vapour  density  measure- 
ments (cf.  p.  179),  obtained  in  some  cases  values  which  were 
multiples  or  sub-multiples  of  the  Berzelian  numbers.  This  and 
the  slender  basis  of  Berzelius'  assumptions  about  the  atomic 
composition  of  compounds  led  most  people  to  despair  of  ever 
finding  the  relative  masses  of  the  actual  atoms,  and  a  strong 
reaction  set  in  against  his  interpretation  of  the  atomic  doctrine. 

Between  1830-50  further  confusion  arose.  Gmelin,  a  Ger- 
man worker,  insisted  on  taking  the  simplest  empirical  com- 
bining ratios  as  the  equivalents  and  neglecting  atomic  weights 
altogether,  thus  halving  nearly  all  the  Berzelian  values.  A 
few  years  later  Gerhardt  noted  that  on  this  hypothesis  more 
than  one  equivalent  of  water  or  carbonic  acid  always  resulted 
when  one  equivalent  of  an  organic  compound  was  burnt,  so  he 
decided  for  the  old  numbers,  except  that  he  regarded  all  metallic 
oxides  as  composed  of  two  atoms  of  metal  and  one  of  oxygen. 
All  three  systems  were  used  concurrently  by  different  workers, 
and  a  few,  not  content  with  the  muddle,  increased  it  by  calling 
the  equivalent  of  oxygen  8  but  that  of  carbon  1 2  \ 

Atomic  Weights  Berzelius  Berzelius  Final 

(o  =  16).            (1818).  (1826).  Gmelin.     Gerhardt.       Value. 

Hydrogen                       i  i  i  i                  i 

Oxygen                         16  16  8  16  16 

Carbon                          12  12  6  12  12 

Iron   .         .  .       rog  54-5  27  27  56 

Sodium       .  .        93  46-5  23  23  23 


38  A  SHORT  HISTORY  OF  CHEMISTRY 

Fortunately  the  French  chemist  Laurent  (1843)  partially 
cleared  up  the  confusion  by  giving  precise  definitions  to  the 
chief  terms  involved,  namely,  equivalents,  the  mutually  replace- 
able quantities  of  similar  and  similarly  combined  elements 
(consequently  not  always  the  same  for  each  element) ;  atoms, 
the  smallest  particles  participating  in  reactions ;  molecules,  the 
smallest  particles  capable  of  free  existence ;  molecular  weight, 
the  weight  of  a  chemical  substance  occupying  the  same  volume 
as  a  molecule  of  hydrogen.  And  Cannizzaro  in  1858  helped 
still  further  by  summarizing  the  methods  of  atomic  weight 
determination  according  to  reliability  as  follows  : — 

(a)  Vapour-density  determination  of  compounds  as  well  as 
elements. 

(*)  Specific  heat  determinations  j  ^  due  reswvation 
(c)  Isomorphism 

§  6.  The  Periodic  System — The  inquiry  into  the  manner 
of  union  between  elements  to  form  compounds  has  always  been 
closely  accompanied  by  observation  of  the  similarity  or  dis- 
similarity of  the  various  elementary  bodies.  Theories  of  the 
mutual  relations  of  the  elements  have,  since  the  establishment 
of  the  atomic  theory,  developed  along  two  lines  : — 

(a)  Discussion  of  the  ultimate  composition  of  the  atoms,  a 
problem  which  we  survey  a  little  later  (p.  41). 

(b)  Investigation  of  regularities  in  the  chemical  behaviour  of 
the  elements. 

Until  Cannizzaro 's  systematization  of  the  atomic  weight  values, 
only  fragmentary  evidence  of  any  connexion  between  properties 
and  atomic  weights  was  available,  but  instances  of  apparent  rela- 
tions of  this  kind  were  very  soon  noticed  here  and  there,  especially 
by  Dobereiner  of  Jena,  who  in  1829  showed  that  some  series  of 
chemically  analogous  elements  could  be  arranged  in  "  triads  " 
whose  atomic  weights  were  in  approximately  arithmetical  pro- 
gression, e.g.  lithium,  sodium,  potassium ;  calcium,  strontium, 
barium  ;  chlorine,  bromine,  iodine.  It  was  also  seen  that  other 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     39 

triads  of  very  closely  related  elements  possessed  almost  identical 
atomic  weights. 

At  about  this  time  the  "  homologous  series  "  into  which  so 
many  organic  compounds  fall  were  being  outlined,  and  Dumas 
sought  to  show  that  the  atoms  themselves  possibly  formed  in 
some  way  a  series  based  on  somewhat  similar  lines;  other  arith- 
metical regularities  were  pointed  out  by  Odling  in  1864.  The 
idea,  though  ingenious,  was  not  supported  to  any  great  extent 
by  facts. 

There  are  no  other  views  sufficiently  important  to  be  recorded 
until  after  the  atomic  weight  confusion  was  removed  in  1858, 
but  almost  within  a  decade  of  this  advance  the  periodic  classi- 
fication of  the  elements  was  accomplished.  In  its  simplest  form 
this,  which  is  the  basis  of  all  modern  inorganic  theory,  was  stated 
by  Newlands  in  1864 ;  he  showed  that  by  tabulating  the  known 
elements  according  to  increasing  atomic  weights  "  each  eighth 
element,  starting  from  a  given  one,  was  a  sort  of  repetition  of 
the  first "  (the  "  Law  of  Octaves  "),  but  little  serious  attention 
was  paid  to  his  discovery  in  England,  and  the  honour  of  evolv- 
ing the  complete  periodic  system  was  divided  five  years  later 
between  Lothar  Meyer  of  Germany  and  Mendelejew  of  Russia. 

The  former  showed  that  physical  properties  (atomic  volumes) 
and  chemical  properties  (valency)  varied  periodically  in  each 
group  of  eight  elements  and  stated  that  the  properties  of  the 
chemical  elements  are  periodic  functions  of  their  atomic  weights. 
The  latter  drew  up  a  complete  table  of  all  the  elements  known 
at  the  time,  arranged  according  to  the  *'  periodic  law  "  and 
attracted  much  notice  by  the  confidence  with  which  he  used  his 
newly  found  "  law "  to  correct  the  atomic  weights  of  some 
elements  and  to  predict  in  marvellous  detail  the  characteristics 
of  three  elements  at  that  time  unknown.  Both  corrections 
and  predictions  have  been  justified,  the  former  in  the  cases  of 
beryllium,  indium,  and  uranium,  the  latter  by  the  discovery 
of  scandium,  gallium,  and  germanium. 

While  the  usefulness  and  general  correctness  of  the  system 


40  A  SHORT  HISTORY  OF  CHEMISTRY 

have  been  admitted  on  all  hands,  difficulties  have  from  time  to 
time  appeared  and  some  have  not  yet  been  removed.  The  chief 
obstacles  which  have  been  encountered  are  : — 

(a)  The  groups  pass  from  a  strongly  electro-positive  element 
(e.g.  lithium)  through  gradually  decreasing  basic  elements  and 
finally  reach  a  strongly  electro-negative  element  (fluorine),  after 
which,  without  any  gradual  transition,  the  next  element  is  again 
highly  electro-positive. 

(b)  The  analogous  elements  of  approximately  equal  atomic 
weights  (such  as  iron,  cobalt,  nickel)  do  not  find  any  suitable 
place  in  the  table. 

(c)  Some  elements  of  widely  varying  chemical  behaviour  are 
brought  into  close  juxtaposition ;  such  are  the  alkali  metals, 
silver,  copper,  and  gold. 

(d)  Some  closely  related  elements  are  separated  in  the  table  ; 
such  are  silver  and  thallium,  or  barium  and  lead. 

(e)  The  position  of  argon  and  potassium  and  of  tellurium 
and  iodine  according  to  their  properties  is  the  opposite  of  that 
demanded  by  their  atomic  weights. 

These  objections  have  been  partly  met  as  follows : — 

(a)  The  "  new  "  non-valent  gases  of  the  atmosphere  occupy, 
from  their  atomic  weights,  positions  intermediate  between  the 
extreme  electro-positive  and  -negative  elements,  and  Ramsay 
suggested  that  they  form  the  transition  elements  previously 
lacking.  It  will  be  noticed  incidentally,  that  the  original  "  Law 
of  Octaves  "  has  become  a  "  Law  of  Ninths  ". 

(c)  and  (d]  It  is  urged  that  the  resemblances  or  dissimilarities, 
as  the  case  may  be,  of  the  various  elements  concerned  are  on 
the  whole  best  satisfied  by  their  present  positions  in  the  table. 

(e)  Many  are  the  re-determinations  of  the  atomic  weights  of 
tellurium  and  iodine  which  have  been  carried  out  in  the  hope 
of  reversing  their  order.  But  the  consensus  of  the  results  tends 
to  show  that  the  accepted  values  are  correct  and  that  this,  to- 
gether with  the  argon-potassium  anomaly,  must  be  left  at 
present  unexplained. 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     41 

Various  difficulties  have  been  at  one  time  or  another  partly 
removed  by  attempts  to  re-cast  the  system ;  among  such  efforts 
may  be  mentioned  those  of  Johnstone  Stoney  (1888),  Walker 
(1891),  and  Staigmiiller  (1902). 

In  concluding  this  section,  it  must  be  emphasized  that 
Mendelejew's  designation  of  the  periodic  system  as  a  "law"  is 
somewhat  of  an  exaggeration.  The  real  law  which  underlies 
the  system  has  not  been  discovered,  although  it  may  be 
surmised  from  the  results  obtained  in  the  past  few  years,  that 
the  essential  principle  concerned  depends  on  the  constitution  of 
the  atoms  themselves,  upon  which  question  the  electronic  theory 
of  matter  will  no  doubt  in  the  course  of  its  future  development 
throw  considerable  light. 

§  7.  Is  all  Matter  derived  from  one  ultimate  Funda- 
mental Material  ? — When  Dalton's  atomic  weight  numbers 
were  tabulated  with  reference  to  that  of  hydrogen  (the  lightest) 
as  unity,  the  values  for  the  few  elements  then  determined  were 
nearly  all  very  approximately  whole  numbers.  There  has  al- 
ways been  an  instinctive  desire  on  the  part  of  philosophers  to 
make  simple  generalizations  wherever  possible  ;  it  was  natural 
to  think  that  the  heavier  atoms  were  made  up  in  some  way 
of  a  definite  number  of  "  condensed  "  hydrogen  atoms.  The 
suggestion  is  connected  with  the  name  of  Prout  and  first  ap- 
peared in  1815.  For  a  long  while  it  was  regarded  sympathetic- 
ally, then  gradually  the  accumulation  of  evidence  against  it 
changed  the  opinion  of  chemists,  and  for  year.s  now  it  has  been 
the  custom  to  speak  rather  lightly  of  "  Prout's  hypothesis  ".  It 
is  pointed  out  that,  firstly,  the  values  on  which  it  was  based 
(Dalton's  and  T.  Thomson's)  were  hopelessly  inaccurate ;  that, 
secondly,  several  workers  with  a  strong  prepossession  in  its 
favour  set  out  to  gather  evidence  for  its  support  and  returned 
convinced  of  its  untenability  ;  that,  thirdly,  other  workers  have 
tried  to  invent  modified  forms  of  the  hypothesis  and  have 
usually  conspicuously  failed.  And  yet,  in  spite  of  the  cool 
reception  which  Prout's  views  meet  with  at  the  present  time, 


42          A  SHORT  HISTORY  OF  CHEMISTRY 

communications  are  intermittently  appearing  in  the  scientific 
journals  from  observers  who  think  they  have  found  a  means 
of  calculating  the  atomic  weights  of  the  elements  or  of  indi- 
cating how  the  latter  have  been  "  evolved  "  from  a  primordial 
material. 

The  accurate  determination  of  chemical  equivalents  by  Ber- 
zelius  and  others  soon  compelled  the  upholders  of  the  original 
hypothesis  to  shift  their  ground;  and  in  succession  the  half 
and  the  quarter  of  an  atom  of  hydrogen  were  put  forward  as 
the  "  unit  "  of  matter.  This  repeated  subdivision  of  the 
"  unit "  of  course  destroyed  the  original  form  of  the  idea. 
Dumas,  Marignac,  and  Stas  were  three  noted  stoichiometric 
investigators,  each  of  whom  started  to  collect  evidence  to  bear 
upon  Prout's  view,  and  all  concluded  that  there  was  no  such 
simple  relation  subsisting  between  the  elements.  Stas,  indeed, 
executed  a  series  of  researches  which  were  for  all  time  a  model 
of  manipulation  and  skill :  true,  of  late  years  sources  of  error 
have  here  and  there  been  detected  in  them,  but  every  such 
source  of  error  known  to  Stas  at  the  period  of  his  work  (1840- 
65)  was  eliminated  with  perfect  care. 

Dumas,  whose  work  was  a  little  prior  to  that  of  Stas,  and 
who  suggested  that  the  elements  formed  "  homologous  series  " 
among  themselves  similar  to  the  series  of  hydrocarbons,  etc., 
discovered  in  organic  chemistry,  and  also  Pettenkofer  (1850) 
devised  mathematical  formulae  whereby  to  deduce  the  atomic 
weights  of  the  heavier  from  those  of  the  lighter  elements,  but 
such  equations  were  scarcely  approximately  exact. 

A  few  years  subsequently  there  comes  a  division  in  the 
speculations  as  to  the  mutual  relations  of  the  elements.  One 
line  of  thought  was  concerned  solely  with  the  resemblances  in 
properties  of  the  various  elements  and  sought  to  find  a  working 
hypothesis  by  which  to  be  guided  in  the  general  problems 
of  chemistry ;  this  helped  to  lead  to  the  evolution  of  the 
"  periodic  classification  of  the  elements  ".  The  other,  the 
more  speculative  and  philosophical  line  of  thought,  deals  with 


THE  ULTIMATE  CONSTITUTION  OF  MATTER     43 

the  "  genesis  of  matter  "  and  the  constitution  of  the  elements 
themselves. 

It  may  be  said  that  this  problem,  too,  has  been  approached 
from  two  sides  :  spectroscopic  and  electrical. 

For  a  number  of  years  from  about  1865  onwards,  Sir  W. 
Lockyer  made  a  detailed  study  of  the  spectra  of  the  different 
stars  and  found  that  the  hottest  stars  contained  chiefly  hydro- 
gen and  other  gases  (some  then  unknown  terrestrially),  the  less 
hot  stars  contained  the  metals  with  which  we  are  familiar  on 
earth,  and  the  coolest  were  carbonaceous  stars.  Again  Sir 
W.  Crookes,  investigating  the  "rare  earths"  obtained  from 
"  yttria  "  (originally  supposed  to  be  the  oxide  of  one  element, 
yttrium),  split  these  up  into  eight  different  fractions  which  were 
in  almost  every  respect  chemically  alike,  but  gave  different 
phosphorescent  spectra.  The  former  research  seems  to  show 
that  in  star-formation  a  process  of  building-up  of  the  heavier 
elements  from  hydrogen — or  something  lighter — is  going  on  ; 
the  latter  that  there  exist  elements  so  closely  related  as  to  be 
more  like  "varieties"  than  distinct  "species"  of  elementary 
matter.  On  this  basis  Crookes  in  1886  suggested  that  the  old 
doctrine  of  the  unity  of  matter  might  be  true  and  that  all  the 
elements  were  condensation  products  of  a  primary  material, 
"protyle".  The  fact  that  Kayser  and  Runge,  and  others, 
have  recently  shown  mathematical  or  "  harmonic  "  relations 
to  exist  between  the  wave-lengths  of  similar  groups  of  lines 
in  different  elementary  "spectra"  is  held  to  be  further  evi- 
dence of  similarity  in  the  different  atomic  structures. 

On  the  other  hand,  Crookes  opened  up  a  new  line  of  attack 
about  1880  by  studying  the  action  of  electric  discharges  in 
vacuum  tubes.  The  "cathode  rays,"  which  he  was  thus  the 
first  to  study,  have  since  been  characterized  by  Sir  J.  J.  Thom- 
son and  others  as  streams  of  rapidly-moving  matter,  as  particles 
whose  mass  was  about  the  thousandth  part  of  that  of  a  hydro- 
gen atom,  and,  finally,  as  particles  or  atoms  of  electricity,  which 
has  thus  itself  come  to  be  regarded  as  material,  or  rather,  we 


44  A  SrtORt  HISTORY  OF  CHEMISTRY 

recognize  now  that  the  basis  of  matter  is  electrical.  Dr. 
Johnstone  Stoney  named  these  atoms  "  electrons  " — a  name 
which  has  lately  become  very  familiar. 

Now,  since  in  electrolysis,  etc.,  a  definite  amount  of  elec- 
tricity is  always  connected  with  the  liberation  of  an  atom  of 
any  element,  and  also  since  the  "  radio-active  "  metals  break 
down  ultimately  into  these  electrons,  it  has  appeared  natural  to 
regard  the  atoms  of  electricity  as  the  basis  of  the  constitution 
of  the  elements,  and  here  we  come  to  the  most  modern  phase 
of  that  curious  ever-present  speculation  as  to  a  "  primary  form 
of  matter  ". 

Most  people  at  present  regard  the  electron  as  tJie  funda- 
mental "stuff"  of  which  "the  world  is  spun,"  but  views 
differ  as  to  how  the  different  atoms  are  made  from  the  elec- 
trons, and  of  course  there  is  absolutely  no  experimental  evid- 
ence to  show.  From  time  to  time,  suggestions  are  offered ; 
in  1908  Jessup  showed  how  by  addition  of  groups  of  electrons 
to  four  "  protons  "  or  fundamental  elements,  all  the  elements 
in  the  periodic  table  could  be  accounted  for,  either  by  building 
up  or  by  "degradation  "  of  atoms  already  so  formed  ;  in  1909 
Egerton  put  forward  the  most  accurate  method  of  "calcula- 
tion "  of  atomic  weights  yet  devised,  based  on  the  fundamental 
assumption  of  electrons  and  accurate  in  most  cases  to  the 
second  decimal  place  when  compared'  with  the  best  experi- 
mental values  (his  work  only  applied,  however,  to  the  twenty- 
eight  lightest  elements,  and  has  been  disputed,  moreover,  by 
Moir  on  the  ground  that  the  agreements  found  are  due  to 
mathematical  necessity). 

Chemists  have,  therefore,  made  fair  progress  of  late  years 
towards  deciding  the  vexed  question  of  the  "  unity  of  matter," 
but  there  is  still  much  to  be  done.  The  outstanding  points 
of  their  work  in  this  direction  have  now  been  briefly  mentioned, 
and  we  must  leave  the  story  as  it  is — unfinished. 


CHAPTER  IV 

INORGANIC  COMPOUNDS  AND   THE  LAWS  OF 
CHEMICAL  COMBINATION 

§  i.  Chemical  Affinity  and  the  Manner  of  Chemical 
Combination — The  German  alchemist,  Albertus  Magnus, 
seems  to  have  first  suggested  the  name  "  affinity  "  to  express 
the  force  which  leads  certain  chemical  bodies  to  react  with 
certain  others.  Ideas  as  to  the  nature  of  the  force  were  in  those 
times  prolific  and  fanciful ;  Glauber  believed  the  different  sub- 
stances to  "  love  "  or  "  hate  "  each  other,  others  thought  that 
combination  was  effected  by  hooks  or  pointed  prongs  on  the 
ultimate  particles  of  matter.  Some  thought  that  similar  bodies, 
others  that  dissimilar  bodies,  exerted  most  mutual  attraction. 
The  first  scientific  treatment  of  the  problem  occurred  when 
Geoffroy  in  1718  tried  to  construct  "  affinity-tables,"  consisting 
of  lists  of  substances  (acids  and  bases),  in  order  of  increasing  or 
decreasing  affinity  with  respect  to  a  fixed  base  or  acid.  How- 
ever, in  the  phlogistic  era  little  progress  was  made,  because  the 
most  important  factor — mass — was  left  out  of  consideration 
altogether. 

In  1775  Bergmann  practically  stated  that  mass  made  no 
difference  at  all,  for  he  said  that  if,  in  the  case  of  a  substance 
YZ,  the  part  Y  had  more  affinity  for  another  part  X  than  for 
Z,  then,  if  X  be  present,  it  would  become  entirely  united  to 
Y  at  the  expense  of  Z,  by  virtue  of  its  greater  affinity.  On 
the  other  hand,  Wenzel  in  1777  discovered  the  "law  of  mass- 
action  "  (which  did  not  reappear  till  nearly  a  century  later)  by 

45 


46  A  SHORT  HISTORY  OF  CHEMISTRY 

urging  that  the  "  amount  of  chemical  action  is  proportional  to 
the  concentration  of  the  acting  substance  ". 

About  1 80 1,  Count  Berthollet  declared  that  the  predominant 
factor  in  chemical  union  was  the  relative  masses  of  the  sub- 
stances concerned  and  not  their  affinity ;  this  was  of  course  the 
diametrical  opposite  of  Bergmann's  views,  and  was  based  on  his 
conception  (and  men  like  BurTon,  Newton,  and  other  philo- 
sophers, had  held  the  same  idea)  that  the  force  determining 
chemical  action  was  identical  with  gravity.  He,  therefore,  sup- 
posed that  this,  like  gravity,  was  dependent  on  the  masses  of  the 
reacting  compounds,  but  pushed  his  views  too  far  by  imagining 
that  any  (and  not  definitely  "  equivalent ")  masses  of  two  sub- 
stances could  unite  to  form  a  third.  In  the  ensuing  six  years 
Proust  contested  his  view,  and  proved  by  experimental  work  on 
the  basic  carbonates  of  copper,  the  two  oxides  of  tin,  the  two 
sulphides  of  iron,  and  other  compounds,  that  Berthollet  was 
wrong,  that  combination  only  took  place  in  constant  unvarying 
proportions,  and  that  if  two  elements  united  to  form  more  than 
one  compound,  the  composition  varied  by  leaps  from  one  pro- 
portion to  another,  and  never  gradually  passed  from  one  to  the 
other.  The  excellence  of  Proust's  experimental  work  forced 
Berthollet  to  admit  he  was  mistaken,  and  to  modify  his  theory 
accordingly.  In  its  modified  form,  of  course,  it  was  correct,  for, 
as  has  been  increasingly  recognized,  the  mass  of  the  reacting 
substances  present  plays  a  very  important  part  in  determining 
the  course  of  a  reaction. 

Soon  after  this  time  the  close  connexion  between  electricity 
and  chemical  affinity  began  to  be  pointed  out  by  Davy,  Berze- 
lius,  and  others,  but  as  this  concerns  the  structure  of  inorganic 
bodies  rather  than  the  point  we  are  now  studying  we  will  leave 
it  for  a  moment. 

During  the  first  half  of  last  century  the  results  of  numerous 
researches  tended  to  support  the  essential  or  modified  part  of 
Berthollet's  theory.  For  example,  H.  Rose  made  an  extended 
examination  of  the  part  played  by  water  in  various  actions 


INORGANIC  COMPOUNDS  47 

where,  given  suitable  conditions,  it  can  displace  relatively  strong 
acids  (1842) ;  he  showed  how  in  some  cases  (iron,  mercury, 
etc.)  basic  salts  are  formed  in  presence  of  excess  of  water,  while 
in  others  (alkaline  sulphides)  complete  hydrolysis  may  occur. 
Somewhat  later  he  discussed  the  influence  of  the  varying  pro- 
portions of  the  reacting  compounds  in  cases  of  "  double  decom- 
position," and  in  1855  Gladstone  published  important  results 
dealing  with  the  same  class  of  reactions. 

Meanwhile,  in  1850,  Wilhelmy  devised  a  formula  to  express 
the  rate  of  "  inversion  "  or  hydrolysis  of  cane  sugar  which  is 
essentially  an  enunciation  of  the  modem  form  of  the  "  law  of 
mass  action  ".  Further  data  towards  this  end  were  provided  by 
the  elaborate  work  of  Berthelot  and  Pean  de  St.  Gilles  from 
1 86 1  to  1863  on  esterification  ;  they  showed  that,  starting  with 
equimolecular  amounts  of  alcohol  and  acid,  or  of  the  corre- 
sponding ester  and  water,  the  same  mixture  of  alcohol,  acid, 
ester,  and  water  will  finally  be  reached,  and  that  the  final  com- 
position of  this  mixture  can  be  altered  according  to  simple  rules 
by  increasing  the  acting  mass  of  any  of  the  constituents.  On 
the  other  hand,  thermo-chemical  evidence  which,  again,  helped 
to  support  the  law  of  mass-action,  was  given  by  Julius  Thomsen 
at  varying  times  from  1854  to  1868.  The  most  complete  state- 
ment of  the  matter  is  always  associated  with  the  names  of  two 
Norwegian  investigators,  Guldberg  and  Waage.  Supported  by 
the  facts  which  have  just  been  summarized,  and  basing  their 
arguments  on  Berthollet's  proposition  that  "  chemical  equili- 
brium depends  not  only  upon  the  affinity,  but  also  essentially 
upon  the  relative  masses  of  the  reacting  substances  "  (Nernst, 
"  Theoretical  Chemistry "),  they  affirmed  that  in  all  chemical 
actions  the  amount  of  action  is  proportional  to  the  acting  mass. 
Since  we  are  merely  treating  the  subject  historically,  it  is  im- 
possible to  give  the  details  of  their  argument,  but  we  may  repro- 
duce the  familiar  equation  which  represents  the  velocity  V  with 
which  a  given  reaction  will  proceed  : — 


48  A  SHORT  HISTORY  OF  CHEMISTRY 

If  substances  of  concentration  clczc3  .  .  .  are  reacting  to  form  new 
substances  of  concentration  cVV*3  •  •  • 


where  k,  kl  are  numerical  constants  ;  thus  when  equilibrium  is  attained, 


The  treatise  "  fitudes  sur  les  affinites  chimiques"  (1867)  in 
which  these  results  appeared  remained  comparatively  unnoticed 
for  some  time,  and  indeed  the  generalization  was  subsequently 
made  by  other  chemists,  but  in  its  most  extended  form  it  was 
developed,  as  we  have  said,  by  Guldberg  and  Waage.  Van't 
Hoff  (1877)  and  Horstmann  (1869-77)  succeeded  in  making 
approximately  the  same  generalization  in  perhaps  a  more 
strictly  logical  or  deductive  manner  from  thermo-dynamical 
and  mathematical  considerations. 

There  have  been  a  number  of  studies  published  on  the  sub- 
jects of  affinity  and  mass-action  since  the  law  was  definitely  stated 
in  1867  ;  these  are  dealt  with  in  Chapter  x. 

It  will  be  seen  that  the  terms  chemical  statics  and  dynamics 
are  by  no  means  fanciful,  for  nowadays  the  problem  of  chemical 
affinity  has  been  reduced,  so  to  speak,  to  mathematical  equations 
and  numerical  constants,  and  by  such  rigid  means  as  these  a 
knowledge  of  how  the  forces  producing  chemical  charge  act  is 
being  rapidly  gained,  but  when  it  is  asked  what  are  these  forces 
and  why  do  they  so  act,  we  cannot  tell. 

Having  now  outlined  the  work  done  on  the  general  question 
of  the  rules  of  chemical  reaction  and  formation  or  decomposition 
of  compounds,  we  turn  to  the  other  aspect  of  the  problem,  viz. 
how  are  the  various  atoms  joined,  each  to  the  other,  in  chemical 
compounds  ?  It  will  be  convenient  to  restrict  ourselves  for  the 
time  being  to  inorganic  compounds,  for  the  theories  of  the 
structure  of  organic  substances  are  in  a  far  more  advanced  state 
than  those  of  the  former. 

§  2.  The  Structure  of  Inorganic  Compounds  —  The 
purpose  of  this  book  prevents  us  again  from  dealing  with  the 
oldest  views  of  structure,  and  we  must  confine  ourselves  to  the 


INORGANIC  COMPOUNDS  49 

more  modern  facts  and  theories,  which  are  certainly  no  less 
interesting.1 

As  chemists,  however,  we  have  to  pay  attention  to  present 
facts  rather  than  past  fancies  or  future  chances.  The  facts 
upon  which  the  structure  of  compounds  depends  are  primarily 
the  "  laws  "  of  constant  and  multiple  combining  proportions. 
We  will  call  to  mind  then,  how  the  former  was  definitely  proved 
by  Proust  in  1801-7  (P-  4^)>  and  the  latter  also  foreshadowed 
in  Proust's  work  and  definitely  established  by  Dalton  about 
1808  (p.  33).  With  the  united  help  of  these  laws  and  of 
Dalton's  atomic  theory,  it  seemed  so  easy  to  most  chemists  in 
the  early  decades  of  last  century  to  devise  formulae  for  all  manner 
of  compounds.  And  so  it  was,  indeed,  very  easy ;  but  whether 
the  formula  bore  any  relation  to  the  chemical  behaviour  of  the 
compound  in  question  was  often  quite  another  matter,  and  in 
not  a  few  cases  the  older  formulae  absolutely  fail  to  express  the 
facts  at  all.  In  short,  the  problem  of  the  structure  of  inorganic 
compounds  was  for  a  long  while  thought  to  be  much  more  simple 
than  it  really  is. 

The  view  that  there  was  a  mutual  connexion  between  heat, 
electricity,  and  chemical  force  came  to  the  front  about  1800. 
Twenty  years  previously,  Galvani  had  noticed  the  action  of  an 
electric  current  on  the  frog,  and  Volta  had  extended  the  know- 
ledge of  electricity  considerably,  had  devised  his  "  Pile,"  and 
had  suggested  that  friction  of  two  dissimilar  bodies  was  sufficient 
to  endow  them  with  electricity  of  opposite  polarity.  In  1807, 
Davy  elaborated  this  view  by  holding  that  the  smallest  particles 
of  substances  (atoms)  become  oppositely  electrified  upon  con- 

1  There  is  a  curious  attraction  about  the  old  fanciful  notions  of  many  of 
the  alchemists  and  phlogistic  chemists  which  seems  to  make  the  story  of 
their  work  much  more  interesting  to  read  than  that  of  later  and  present- 
day  chemists ;  perhaps  the  underlying  cause  is  the  same  as  that  which 
makes  a  novel  appeal  to  most  people  more  than  a  history  book,  or,  judging 
from  current  magazines,  which  renders  the  possibilities  of  "radium"  or 
"electrons"  more  attractive  to  the  "lay  mind"  than,  shall  we  say,  the 
constitution  of  quinine  or  the  law  of  mass-action, 
4 


So          A  SHORT  HISTORY  OF  CHEMISTRY 

tact  (the  intensity  of  electrification  rising  with  increase  of 
temperature),  and  that  chemical  combination  results  from 
neutralization  of  the  opposing  potentials.  The  sign  of  the 
potential  of  the  combining  elements  could  be  experimentally 
determined,  electro- positive  elements  being  isolated  upon  elec- 
trolysis at  the  negative  pole,  and  vice  versa. 

In  1812,  and  more  fully  in  1819,  Berzelius  published  the 
dualistic  theory  of  chemical  combination,  which  resembled 
Davy's  in  some  fundamental  points,  but  differed  in  that  it  was 
more  systematically  developed.  He  assumed  that  every  atom 
possesses  both  +  ve  and  —  ve  electricity,  but  in  varying  amounts. 
Thus  some  elements  were  positive,  others  negative,  most  were 
positive  with  respect  to  some,  and  negative  with  reference  to 
other  elements  ;  oxygen  only  was  never  positive  to  any  element, 
and  so  was  held  to  be  purely  electro-negative,  and  for  this  and 
other  reasons  was  adopted  by  Berzelius  as  his  standard  or  starting- 
point.  The  elements  by  combination  furnished  new  bodies  in 
which  again  an  excess  of  one  or  other  kind  of  electricity  was 
present.  Thus  basic  oxides  came  from  the  union  of  oxygen 
and  strongly  electro-positive  elements  (metals),  and  acid  oxides 
from  oxygen  and  the  metalloids.  This  tended  to  confirm 
Lavoisier's  view  (p.  26),  that  all  acids  contain  oxygen.  Salts, 
and  furthermore  mixed  salts  and  hydrated  salts,  were  regarded 
as  the  product  of  union  of  the  already  compound  bases  and 
acids,  an  excess  of  one  or  other  kind  of  electricity  being  always 
left  over,  but  in  less  pronounced  quantity  than  with  simpler 
substances.  This  important  theory  served  well  to  point  out  the 
constitution  of  the  most  obvious  classes  of  inorganic  compounds, 
viz.  bases,  acids,  and  salts.  Berzelius,  however,  tried  to  push 
it  further  and  attempted  to  systematize  the  organic  compounds 
then  known  on  the  same  basis.  Until  about  1840  his  efforts 
met  with  complete  approval,  and  the  dualistic  theory  held 
practically  universal  sway.  Soon  afterwards  it  began  to  de- 
cline, chiefly  through  the  influence  of  the  following  facts  : — 

(i)  In  1834  Dumas  discovered  the  phenomena  of  "substitu- 


INORGANIC  COMPOUNDS  51 

tion  "  in  organic  chemistry,  by  which  a  strongly  negative  element 
(chlorine)  replaced  electro-positive  hydrogen. 

(2)  In  1839  Daniell  showed  that  in  the  course  of  electrolysis 
the  same  amount  of  electricity  will  set  free  a  definite  amount  of 
hydrogen  on  being  led  successively  through  water  and  a  solution 
of  sodium  sulphate,  but  also,  in  the  latter  case,  will  liberate  an 
equivalent  of  sodium  hydrate,  thus  doing  double  as  much  work 
in  the  second  as  in  the  first  instance,  according  to  Berzelius' 
theory. 

(3)  The  dualistic  hypothesis  did  not  precisely  explain  why 
certain  acids  not  containing   oxygen  (notably  HC1)    were  as 
strong  or  stronger  than  many  oxygen  acids,  containing  the  most 
electro-negative  element  of  all. 

Many  objections  to  the  dualistic  theory  therefore  arose 
about  1845-50,  and,  as  usual,  the  reaction  carried  opinion  to 
the  other  extreme,  and  it  was  sought  to  regard  inorganic  com- 
pounds as  simply  composed  of  the  different  "units"  of  atoms, 
in  a  similar  manner  to  the  way  in  which  the  structure  of  organic 
substances  was  beginning  to  be  regarded  at  that  time.  The 
French  chemists,  especially  Dumas  and  Wurtz,  took  the  most 
prominent  part  in  developing  the  "unitary,"  as  opposed  to  the 
dualistic,  idea. 

§  3.  Valency — This  word  is  synonymous  with  the  terms 
"  replaceable  value,"  "  atomicity,"  "  saturation-capacity,"  and, 
like  some  other  terms  occurring  at  different  periods  of  chemical 
history,  it  has  tended  to  become  somewhat  of  a<  nuisance  and  to 
enforce  conceptions  entirely  beyond  its  real  simple  meaning. 
It  is  a  name  for  the  "  combining  worth  "  of  an  element,  ex- 
presses the  number  of  equivalents  of  a  "  univalent  "  element 
with  which  the  element  in  question  can  unite,  and,  as  E.  Meyer 
has  said,  is  really  nothing  more  than  an  expression  of  the  laws 
of  definite  and  multiple  combining  proportions. 

In  1834  Dumas  showed  in  connexion  with  his  substitution 
researches  that  one  "  atom  "  of  chlorine  replaced  one  atom  of 
hydrogen,  but  that  the  latter  was  replaced  by  only  a  "  half  atom  " 


52  A  SHORT  HISTORY  OF  CHEMISTRY 

«^£oxygen.  A  little  later  Liebig  noted  that  an  antimony  atom 
canbf  mbine  with  three  atoms  of  hydrogen,  whereas  the  potas- 
siunf  atom  is  equivalent  to  only  one,  and  he  also  developed  the 
knowledge  of  polybasic  acids,  showing  that  some  acids  contain 
only  one  and  others  (e.g.  citric  acid)  more  than  one  replace- 
able hydrogen  atom.  This  brings  out  the  idea  of  the  equivalent 
as  distinct  from  atom  or  molecule,  and  in  1843  Laurent  gave 
definite  expression  to  the  term,  and  stated  that  elements  could 
possess  varying  equivalents  under  varying  conditions. 

The  idea  of  a  constant  combining  worth  for  each  element 
was,  however,  very  popular  in  those  days,  and  Wurtz,  for  ex- 
ample, formulated  numbers  of  inorganic  compounds  on  the 
hypothesis  that  the  elemental  valencies  were  always  fixed.  Such 
formulae,  which  quite  failed  to  represent  the  chemical  behaviour, 
and  were  simply  strings  of  letters,  such  as  HOOOC1  for  chloric 
and  HOOOOC1  for  perchloric  acid  (to  give  only  one  instance), 
prevailed  in  "  text-books  "  for  many  years,  and  have  not  abso- 
lutely died  out  even  at  the  present  day.  Kolbe  wrote  in  favour 
of  a  "maximum  valency  "  of  each  element  in  1854 — indicating 
the  existence  of  possible  cases  where  all  the  "  valencies  "  were 
not  utilized.  At  about  the  same  time  papers  were  being  pub- 
lished on  the  subject  in  England  by  Williamson  and  by  Odling. 
Williamson's  work  was  more  concerned  with  the  constitution  of 
organic  compounds  (cf.  chap,  vi.),  while  Odling  discussed  the 
different  combining  powers  of  iron  and  tin,  as  shown  in  their 
varying  oxides,  and  introduced,  by  the  way,  the  term  "  replace- 
able value  ".  His  adhesion  to  the  "  type  "  theory  of  organic  com- 
pounds, by  means  of  which  he  tried  to  classify  inorganic  acids, 
presumably  prevented  him  from  arriving  at  such  conclusions  as 
those  deduced  by  another  English  chemist,  Frankland.  It  is  to 
the  latter,  indeed,  that  the  clearest  ideas  about  valency  at  this 
period  are  due.  This  work  dates  from  about  1853  onwards, 
and  his  views  were  generally  accepted  by  the  year  1860.  He 
noted  how  nitrogen,  phosphorus,  antimony,  and  arsenic  behaved 
sometimes  as  tervalent  and  sometimes  quinquevalent,  and  was, 


INORGANIC  COMPOUNDS  53 

therefore,  led  to  regard  them  as  analogous  ;  for  similar  reasons 
he  classed  carbon,  silicon,  titanium,  and  zirconium  togethei>e< 
He  did  more  than  any  of  the  contemporary  workers  forgive 
a  definite  meaning  to  "valency"  or  "  saturation-capacity,"  as 
he  called  it  :  he  showed  how  circumstances  influenced  the 
combining  capacity  of  the  elements,  so  that  an  element  which 
under  given  conditions  evinced  no  tendency  to  behave  otherwise 
than,  say,  tervalent  might,  in  other  cases  possess  anbtb^r 
valency.  He  argued  that  such  substances  would  p«sess  *  a 
maximum  "  saturation-capacity,"  but  that  all  its  possible  "  valen- 
cies "  would  not  invariably  come  into  action.  This  method  of 
classifying  elements  according  to  similar  combining  power  was, 
of  course,  a  step  in  the  direction  of  the  "  periodic  classification," 
which  we  have  already  discussed  (p.  38). 

On  the  Continent,  on  the  other  hand,  events  moved  some- 
what differently.  Gerhardt  put  forward  views  similar  to  Frank- 
land's  as  early  as  1856,  but  in  1860  Kekule,  arguing  from  the 
"  organic  "point  of  view,  declared  for  the  principle  of  constant 
valency.  Blomstrand,  Kolbe,  and  others  debated  the  point 
during  the  next  five  years,  the  result  being  the  confirmation  of 
Frankland's  theory.  Erlenmeyer,  about  1863,  made  an  im- 
portant statement,  which  was  in  the  main  the  same  as  Frank- 
land's,  but  extended  the  latter  by  the  conception  that  valency 
was  due  to  the  number  of  "  points  of  affinity  "  possessed  by 
each  element.  This  has  had  a  somewhat  unfortunate  sequel, 
for  it  is  probably  the  innocent  cause  of  the  excessive  emphasis 
which  has  so  often  been  laid  on  the  modern  "  structure-for- 
mulae," in  which  union  is  depicted  by  dashes.  It  is  interesting 
to  speculate  how  many  people  have  consciously  or  uncon- 
sciously conceived  the  dashes  as  an  image  of  the  real  mode  of 
union  of  atoms.  The  signs  mean  nothing  except  that  one  atom 
is  "united"  with  the  next — how  precisely  no  one  knows. 

The  point  as  to  whether  all  the  affinities  of  a  polyvalent  ele- 
ment are  of  equal  worth  has  been  pretty  thoroughly  discussed 
since  the  modern  idea  of  valency  took  firm  hold.  The  experi- 


54  A  SHORT  HISTORY  OF  CHEMISTRY 

mental  investigation  has  centred  round  derivatives  of  carbon 
(Roscoe  and  Schorlemmer,  Henry  (1888)),  sulphur  (Kruger, 
Klinger),  and  nitrogen  (hydroxylamine  derivatives,  etc.,  by 
Lossen,  Beckmann). 

This  simple  conception  of  valency,  however,  is  not  enough  to 
explain  many  facts  which  have  come  to  light  of  late  years.  These 
new  points  generally  concern  the  structure  of  organic  bodies, 
but  for  the  sake  of  compactness  will  be  presented  here.  The 
reactions  of  substances  written  asR.CH  =  CH.CH  =  CH.R1 
are  quite  anomalous  according  to  this  formula  ;  on  reduction  or  ad- 
dition of  halogen  they  yield  R.  CHX.  CH  =  CH.  CHX.  R1 
exclusively,  and  not  R  .  CHX  .  CHX  .  CH  =  CH  .  R1.  In  1899 
Thiele  suggested  that  the  affinities  of  elements  were  not  always 
completely  utilized,  that  in  "unsaturated  "  compounds,  com- 
pounds possessing  "  residual  affinity,"  the  carbon  must  be  repre- 
sented as  possessing  "  partial  valencies,"  and  that  a  better 
method  of  graphically  representing  them  was 

R.CH  =  CH—  CH  =  CH.R1. 


Assuming  that  the  central  "  partial  valencies  "  saturated  each 

other  he  arrived  at  the  formula 

R.CH  =  CH—  CH  =  CH.RWR.CHX.CH  =  CH.CHX.R1. 


Again,  complex  salts  of  various  metals  are  known  which 
cannot  be  readily  accounted  for  by  the  simple  valence  theory. 
Werner  has  advanced  the  view  that  such  compounds  (cobaltam- 
mines,  cobalticyanides,  etc.  etc.)  must  be  represented  by  a  new 
method.  Taking  a  concrete  example,  the  following  cobaltam- 
mine  chlorides  are  known,  the  chlorine  atoms  outside  the  bracket 
being  the  only  ones  which  become  ionized  in  solution  : 
[Co(NH3)6]Cl3,  [Co(NH3)5Cl]Cl2,  [CoCl2(NH3)JCl,  and, 
finally,  non-ionized  bodies,  such  as  [Co(NH3)3(NO2)3].  So 
far,  as  Blomstrand  and  Jorgensen  showed  long  ago,  there  is  no 
need  to  go  beyond  ordinary  structure  formulae,  but  some  com- 


INORGANIC  COMPOUNDS 


55 


pounds  of  the  type  [Co(NH3)4R.2]X  each  exist  in  two  different 
forms,  of  characteristic  colour.  Werner  attributes  this  to  a 
new  kind  of  stereoisomerism  of  the  group  within  the  square 
brackets  thus  : — 


R 

I   NH3 

NH,— CO— NH, 


NH3 


and 


NH3 
NH3 

NH3— CO— NH3 
R 


This  mode  of  union  he  calls  "co-ordination,"  to  distinguish  it 
from  the  usual  union,  expressed  in  terms  of  ordinary  "  valency  ". 
Jorgensen,  however,  disputes  the  method  of  representation  en- 
tirely, and  since  doubt  also  exists  as  to  the  correctness  of  some 
of  the  alleged  observed  facts,  the  matter  must  be  left  at  this 
point.1 

The  whole  subject  of  valency  is  thus  still  very  unsettled ;  it 
seems  of  late  years  as  though  the  solution  of  the  problem  will 
ultimately  be  upon  an  electrical  or  electronic  basis. 

In  1904  Abegg  put  forward  the  view  that  each  element  is 
potentially  octovalent,  the  eight  valencies  being  made  up  of 
positive  and  negative  ("normal"  and  "  contra ")  valencies,  as 
follows : — 


Periodic  Table 
Group. 
Normal 
Contra 


+  i 
-  7 


II. 

+  2 

-  6 


III. 

+  3 
-  5 


IV.        V.        VI.        VII. 


+  4 
-  4 


'-3 

+  5 


-  2 

+  6 


-  i 

+  7 


The  extent  to  which  the  contra-valencies  come  into  play 
depends  partly  on  the  nature  of  the  atom  itself,  partly  on  the 
circumstances  of  its  combination.  This  hypothesis  is  more  or 
less  a  precursor  of  the  purely  electronic  view. 

1  Other  views,  involving  less  profound  modification  of  existing  ideas 
on  valency,  have  been  recently  put  forward  by  Friend  (1908),  Sir  William 
Ramsay  (1908),  and  Miss  Baker  (1909),  in  order  to  explain  the  structure 
of  the  metallammino  derivatives, 


56  A  SHORT  HISTORY  OF  CHEMISTRY 

In  1907  Sir  J.  J.  Thomson  suggested  that  elemental  valency 
depends  on  the  transference  of  electrons  to  or  from  the  element 
atoms  by  the  action  of  other  element  atoms,  so  that  the 
"  valency  lines  "  really  portray  tubes  of  electric  force  towards 
or  away  from  the  atom.  This  view  is  being  extended  to  the 
structure  of  organic  compounds,  and  it  is  evident  that  it  marks 
an  advance  upon  the  older  theories,  since  it  is  a  step  in  the 
direction  of  a  hypothesis  which  may  eventually  present  an 
explanation  of  all  the  varied  problems  of  chemical  structure 
and  unite  them  into  one  simple  theory.  At  present  it  appears 
difficult  to  get  enough  experimental  evidence  upon  which  to 
base  an  universal  electronic  theory  of  chemical  composition. 

§  4.  Electro-chemical  Theories— It  will  be  best  to  give 
at  this  point  a  collected  account  of  the  various  hypotheses 
developed  during  the  last  hundred  years  with  reference  to 
electro-chemical  decomposition.  The  general  electrical  theories 
of  Davy  (1807)  and  Berzelius  (1812-40)  have  already  received 
attention  (pp.  49,  50),  but  the  more  particular  explanation  of 
the  phenomena  of  electrolysis  remains  to  be  dealt  with. 

The  theory  which  found  its  way  into  text-books  for  many 
years  was  that  of  Grotthus  (1805),  according  to  which  the 
electrolyte  molecules,  previously  indiscriminately  distributed 
through  the  solution,  arranged  themselves  in  "  chains  "  through 
the  liquid  under  the  influence  of  the  electric  current,  the  par- 
ticles adjacent  to  the  electrodes  then  separating,  thus  : — 

Current 


In  1854  Clausius  applied  the  kinetic  theory  (which  he  had 
recently  developed  in  the  case  of  gases)  to  electrolysis.  He 
assumed  that  the  electrolyte  molecules  were  in  constant  motion 
in  the  solution  (a  view  previously  expressed  in  more  general 


INORGANIC  COMPOUNDS  57 

terms  by  Williamson  in  his  work  on  the  ethers  ;  cf.  p.  84),  and 
that  consequently  they  were  momentarily  split  up  into  their  ions 
(to  use  the  convenient  modern  term).  Under  ordinary  circum- 
stances recombination  took  place  at  once,  but  in  presence  of 
a  current  the  ions  were  separated  at  the  electrodes,  a  mutual 
interchange  of  component  parts  ensuing  between  the  dissolved 
molecules  between  the  electrodes.  The  objection  to  both 
theories  is  that  each  presupposes  a  certain  minimum  electric 
force  to  be  necessary  for  electrolysis,  whereas  the  smallest 
current  will  effect  electrolytic  decomposition. 

The  next  great  advance  was  the  "ionic  theory  "  of  electro- 
lysis, established  by  Arrhenius  in  1887,  and  foreshadowed  as 
early  as  1833  by  Faraday.  The  latter  scientist  outlined  the 
two  chief  "  laws  "  of  electrolysis  (the  amount  of  chemical 
action  is  proportional  to  the  amount  of  electricity,  and  chemic- 
ally equivalent  quantities  of  all  ions  are  set  free  by  the  same 
quantity  of  current),  introduced  the  terms  "ion,"  "anion," 
"cation,"  and  was  convinced  that  "the  power  which  governs 
electro-chemical  decomposition  and  ordinary  chemical  attrac- 
tions is  the  same,"  and  that  the  force  acting  upon  the  ions 
was  "either  superadded  to  or  giving  direction  to  the  ordinary 
chemical  affinity  ". 

Arrhenius  supposed  that  all  electrolytes  (according  as  they 
are  "good"  or  "bad"  conductors)  are  more  or  less  dissociated 
in  solution  into  ions  carrying  charges  of  "positive"  or  "nega- 
tive "  electricity  in  proportion  to  their  "  valency  ".  The  electric 
current  simply  acts  as  a  directing  force,  causing  the  ions  to 
migrate  to  either  electrode  and  then  to  deposit  their  electric 
charges,  after  which  they  reappear  as  the  usual  chemical 
elements  or  groups,  and  may  be  then  set  free  as  such,  or 
undergo  further  chemical  decomposition  with  the  electrode  or 
the  solution.  This  view  found  great  support  from  other  physico- 
chemical  evidence,  notably  when  Ostwald  showed,  by  widely 
extended  instances,  that  the  electrical  conductivity  or  affinity 
coefficient  of  acids  and  bases  gave  exactly  the  same  order  of 


58  A  SHORT  HISTORY  OF  CHEMISTRY 

strength  as  that  determined  by  a  variety  of  physical  and 
chemical  methods  (cf.  p.  177). 

Another  modern  theory  of  electrolysis,  the  "  hydrate " 
theory,  must  also  be  mentioned,  but  this  is  not  apparently 
destined  to  have  a  great  influence  on  chemical  theory. 

The  latest  advances  deal  with  the  extension  of  the  ionic 
theory,  owing  to  the  conception  of  the  materialistic  nature  of 
electricity.  When  "  negative  "  electricity  was  first  shown  to  be 
material,  it  was  naturally  anticipated  that  there  would  be  a 
corresponding  "  positive  "  electricity  as  well,  but  later  work 
points  to  the  conclusion  that  there  is  only  one  kind  of  elec- 
tricity— "  negative  electricity,"  or,  using  modern  terminology, 
electrons.  Consequently  a  certain  amount  of  readjustment  of 
the  theories  of  electrolysis  has  become  necessary,  and  this  has 
lately  been  effected,  notably  by  Ramsay  (Presidential  Addresses 
to  the  Chemical  Society,  1908-9).  It  is  suggested  that  the 
elementary  atoms  are  combined  with  electrons  in  two  ways — 
with  "active "and  with  " latent"  electrons.  The  number  of 
latent  electrons  depends  on  the  maximum  valency  of  the  ele- 
ment and  the  particular  valency  displayed  in  a  given  instance, 
while  the  active  electrons  are  the  cause  of  the  displayed 
valency. 

Suggestions  of  a  somewhat  similar  kind  have  also  been  made 
recently  by  Kauffmann,  Stark  and  other  chemists.  Stark's 
view  of  the  process  involves  the  assumption  that  neutral  water 
molecules  are  added  to  the  ions,  and  thus  accounts  for  the 
phenomena  of  hydration  of  the  ions. 


CHAPTER  V 

NOTES  ON  THE  HISTORY  OF  THE  ELEMENTS 
AND  THEIR  CHIEF  COMPOUNDS 

HAVING  discussed  the  general  development  of  our  views  relating 
to  the  nature  of  elements  and  the  manner  of  their  chemical 
combination,  we  must  devote  a  few  pages  to  a  description  of 
the  chief  inorganic  substances.  In  some  cases  there  are  in- 
teresting points  connected  with  the  discovery  of  an  element  or 
the  production  of  a  new  compound,  but  as  a  rule  the  discovery 
of  a  particular  substance  is  of  very  minor  importance  when  com- 
pared with  the  principles  governing  the  work  in  question  or 
with  the  systematization  of  a  class  of  compounds  or  of  chemical 
reactions.  We  shall  accordingly  pay  greater  attention  to  the 
latter  two  lines  of  research,  giving  at  the  same  time  incidental 
prominence  to  the  history  of  individual  substances.  The  con- 
fusion, prior  to  about  1790,  between  elements  and  compounds— 
has  been  previously  mentioned,  so  that  it  will  be  readily  under- 
stood that  although  numerous  inorganic  or  mineral  substances 
were  known  long  before  that  date,  their  systematic  history  only 
commences  with  Lavoisier,  who  classified  mineral  bodies  into 
acidic  and  basic  oxides,  salts  and  elements.  We  will  review 
them  in  this  order,  adding  further  sections  upon  the  develop- 
ment of  mineralogy,  and  the  comparatively  recent  advances  in 
radio-activity  and  the  knowledge  of  the  metals  of  the  "rare 
earths  ". 

§  i.  Acidic  Oxides — When  Lavoisier  overthrew  the  phlo- 
giston theory  he  established  in  its   place  a  system  in  which 

59 


60  A  SHORT  HISTORY  OF  CHEMISTRY 

oxygen  played  much  the  same  part  as  the  hypothetical  "  phlo- 
giston "  in  the  preceding  era — oxygen  was  the  central  point  of 
his  chemical  system,  since  it  united  with  every  element  known 
to  him.  Referring  to  his  system  of  nomenclature  (p.  30),  we 
see  that  he  called  the  compounds  of  the  metals  with  oxygen, 
oxides  or  bases,  while  those  of  oxygen  and  the  metalloids 
("  non-metals  ")  were  termed  acids.  He  held  oxygen  to  be  an 
essential  constituent  of  all  acids,  and  gave  it  its  name  (acid 
producer)  accordingly.  Berzelius  modified  these  views  by  as- 
suming that  oxygen  was  the  most  electro-negative  element,  all 
others  being  electro-positive  with  respect  to  it.  The  acidic  or 
basic  properties  of  the  oxides,  therefore,  depended  upon  the 
excess  of  negative  electricity  possessed  by  the  oxygen  or  of 
positive  electricity  possessed  by  the  combining  element;  this 
view  again  required  the  presence  of  oxygen  in  all  acids. 
The  halogen  acids,  such  as  hydrochloric  (muriatic)  were  sup- 
posed to  be  compounds  of  hydrogen  and  a  halogen ;  the 
latter  substances  were  assumed  to  be  oxides  of  hypothetical 
elements.  However,  since  the  halogens  had  never  been  split 
up  into  simpler  substances,  they  were,  according  to  Lavoisier's 
definition  of  an  element,  elements,  and  efforts  were  soon  made 
in  the  case  of  chlorine  to  decide  whether  it  was  really  a  com- 
pound. About  1810  Gay-Lussac  and  Thenard,  in  France, 
and  Davy  in  England,  made  attempts  to  decompose  that  gas  in 
various  ways,  but  without  any  success,  and  Davy  decided  that 
it  was  an  element,  and  gave  it  its  present  name  in  distinction  to 
Berthollet's  misleading  title  of  "  oxymuriatic  acid  ".  He  pointed 
out  that  in  the  following  three  reactions  it  behaved  exactly  like 
an  elementary  substance  : — 

i  vol.  Hydrogen  +  i  vol.  Chlorine  —>  2  vols.  Hydrochloric  Acid, 
i  vol.  Hydrochloric  Acid  +  Sodium  ->  Common  Salt  +  £  vol.  Hydrogen. 
Sodium  +  Chlorine  — $>  Common  Salt. 

Gay-Lussac   and  Thenard   also   adopted   this  opinion,    but 
Berzelius  held  out  against '  it  for  a    long  while.     It  naturally 


NOTES  ON  THE  HISTORY  OF  ELEMENTS      61 

spoiled  the  oxygen-acid  theory;  it  helped  to  overthrow  the 
dualistic  hypothesis. 

Davy  himself,  as  a  matter  of  fact,  stated  that  hydrogen 
and  not  oxygen  was  the  essential  constituent  of  acids,  since 
anhydrides  (e.g.  iodic  anhydride)  were  not  acid  except  in 
presence  of  water. 

The  next  notable  point  in  the  history  of  acids  came  several 
decades  later,  and  consisted  of  Graham  and  Liebig's  work 
(already  referred  to,  p.  52).  Graham  showed  that  phosphoric 
and  arsenic  acids  each  exist  in  three  forms,  according  to 
whether  one,  two,  or  three  molecules  of  water  were  combined 
with  one  molecule  of  the  acid  anhydride.  Liebig  proved  a 
similar  fact  a  little  later,  when  he  showed  that  many  organic 
acids  (citric,  cyan  uric  etc.),  were  poly  basic.  In  this  case  the 
dualistic  explanation,  based  on  the  addition  of  fresh  molecules 
of  water,  was  cumbrous,  and  Liebig  soon  saw  that  a  clearer 
view  was  obtained  by  the  hydrogen-acid  theory,  the  polybasi- 
city  being  explained  by  the  presence  of  more  than  one  re- 
placeable hydrogen  atom.  This  was  really  the  first  contribution 
to  the  modern  theory  of  valency. 

After  the  general  adoption  of  the  hydrogen-acid  theory 
(about  1855)  there  is  little  to  be  recorded  in  the  development 
of  views  in  this  direction,  except  that  Arrhenius'  ionic  theory 
extends  the  conception  still  further  by  suggesting  that  the 
'characteristic  properties  of  acids  are  due,  not  to  elementary  but 
to  ionic  hydrogen,  H+.  At  the  present  day.  the  most  general 
definition  of  an  acid  is  a  substance  containing  hydrogen  re- 
placeable by  metals,  an  expression  which  includes  many  organic 


__  CO\ 

bodies  (e.g.    phthalimide     |  .     1  _          NH,      malonic    ester 

~~ 


CH2(COOC2H5)2,  etc.),  and  also  such  metallic  hydroxides  as 
A1(OH)3,  Zn(OH)2,  etc.,  which  form  sodium  salts  in  presence 
of  alkali. 

The  following  acids  deserve  special  attention  :  —  • 


62  A  SHORT  HISTORY  OF  CHEMISTRY 

Sulphurous. — Properties  of  burning  sulphur  known  to  Homer  and  Pliny ; 

SO2  isolated  by  Priestley. 
Sulphuric. — Known  to  Geber ;  preparation  from  iron  vitriol  described  by 

Basil  Valentine. 
Nitric. — Known  to  Geber ;  method  of  preparation  by  Basil  Valentine ; 

constitution  due  to  Cavendish. 

Carbonic. — Known  as  a  distinct  gas  to  Paracelsus  and  v.  Helmont ;  con- 
stitution due  to  Black  and  Priestley. 
Muriatic. — Known  to  Basil  Valentine  (spiritus  salts) ;  preparation  from 

salt  and  vitriol  by  Glauber. 
Aqua  regia. — Known  as  a  mixture  of  aqua  fords  and  spiritus  salis  to 

Basil  Valentine. 
Phosphoric. — Discovered    by    Boyle    (1693) ;  investigated   by   Marggraf, 

Scheele,  Gahn. 

Boric. — First  prepared  and  its  salts  characterised  by  Homberg  (1702). 
Hydrofluoric. — Used  for  etching  glass  by  Schunhardt  (seventeenth  cen- 
tury), but  without  knowing  its  constitution ;  worked  out   by   Gay- 
Lussac  and  Thenard,  Berzelius,  Ampere;  first  prepared  pure  in  1869 
by  Fremy. 

The  acids  and  anhydrides  of  chlorine  (HC1O,  HC1O3,  HC1O4)  were 
investigated  by  Davy,  Balard,  Roscoe  and  others  during  the  first  half  of 
last  century,  but  it  is  comparatively  recently  that  their  constitution  and 
that  of  other  halogen  oxy- acids  has  been  systematically  explained  by  the 
progressive  increase  in  valency  (from  one  to  seven)  of  the  halogen. 

The  majority  of  the  more  complicated  inorganic  acids  (ferrocyanic, 
sulphocyanic,  polythionic,  etc.)  have  only  been  studied  within  the  past 
century.  Gay-Lussac  and  Davy  were  among  the  first  workers  in  this 
field ;  Balard,  Liebig,  Wohler,  and  Roscoe  are  other  prominent  names 
which  must  be  mentioned.  Attention  should  be  paid  to  the  numerous 
researches  on  "  per  "  acids  (cf.  p.  72)  carried  out  during  the  last  few 
decades. 

§  2.  Basic  Oxides  and  Metallic  Salts — The  knowledge 
of  metallic  oxides  has  for  the  most  part  grown  parallel  with  that 
of  the  acids ;  the  characteristic  properties  of  alkalies  (the 
stronger  bases)  were  known  to  the  'earliest  alchemists,  while 
Lavoisier  defined  bases  as  the  oxides  of  the  metals,  and  Berzelius 
assumed  them  to  be  substances  in  which  the  electro-positive 
strength  of  the  metal  overcame  the  electro-negative  force 
exerted  by  the  oxygen.  The  possibility  of  polyacid  bases  fol- 
lowed as  soon  as  the  doctrine  of  polybasic  acids  was  established 


NOTES  ON  THE  HISTORY  OF  ELEMENTS      63 

by  Graham  and  Liebig,  while  finally,  with  the  advent  of  the 
ionic  theory,  the  characteristic  reactions  of  bases  were  seen  to 
depend  on  the  presence  in  solutions  thereof  of  the  hydroxyl 
ion  OH~.  The  term  "  base  "  extends  of  course  to-day  to  all 
substances  capable  of  possessing  such  an  ionizable  hydroxyl 
group,  for  instance,  ammonium  hydroxide  NH4OH,  pyridinium 

/°\ 
HC      |      CH 

C5H5NH.OH,  sulphonium  hydroxides  R3S(OH),      II  — O-  I 

HC  CH 

\c^ 

phosphines  R3P,  py rones  and  so  on. 

Curiously  enough,  the  modem  view  of  a  salt  was  practically 
arrived  at  during  the  phlogistic  period  through  the  work  of 
Rouelle  and  Richter.  Rouelle  (1744)  defined  salts  (neutral, 
acidic,  and  basic)  as  the  substances  formed  by  the  union  of  an 
acid  and  an  alkali,  and  Richter  (1791)  discovered  the  laws 
governing  the  neutralization  of  acids  and  bases  (cf.  p.  32).  It 
was  therefore  simply  necessary  for  Lavoisier  to  adjust  the  terms  to 
his  new  oxygen  theory,  and  to  point  out  that  in  his  system  salts 
were  ternary  and  not  binary  compounds  like  the  acidic  and 
basic  oxides.  Berzelius  also  explained  salt-formation  as  the 
result  of  the  union  of  electro-positive  and  -negative  oxides, 
pointing  out  the  apparent  confirmation  of  his  theory  in  the 
electrolytic  resolution  of  salts  (such  as  sodium  sulphate)  into 
acid  and  alkali.  He  tried  to  account  for  double  salt  formation 
and  the  existence  of  water  of  crystallization  by  the  assumption 
that  even  in  salts  there  remained  a  slight  excess  of  one  or  other 
kind  of  electric  polarity.  The  final  modern  view  of  salt  for- 
mation may  be  illustrated  by  the  typical  ionic  equation  : — 

R++  OH  -  +  H+  +  X~  =-R+  +  X"  +  H2O. 
base  acid  salt 

Before  glancing  at  a  few  bases  and  salts  of  historic  interest, 
we  may  discuss  the  relations  of  the  alkaline  carbonates  to  the 


64  A  SHORT  HISTORY  OF  CHEMISTRY 

alkalies.  This  was  a  source  of  great  misunderstanding  to  the 
alchemists  and  phlogistonists,  many  of  whom  seemed  to  look 
upon  the  alkaline  carbonates  as  elementary  bodies  which  passed 
into  the  alkalies  (alkaline  calces),  e.g.  :  — 

Chalk  +  phlogiston  — >  lime. 

Lime  (i.e.  chalk  +  phlogiston)  +  potassium  carbonate  — $>  caustic  potash 
+  chalk. 

The  researches  of  Joseph  Black  (1755)  cleared  up  the  whole 
matter,  for  he  showed  that : — 

(a)  Limestone  or  chalk  lost  weight  by  calcination  and  yielded  a  gas 

("fixed  air")  identical  with  van  Helmont's  "  gas  sylvestre". 

(b)  The  "  mild  alkalies  "  (alkaline  carbonates)  could  also  be  made  to 

yield  this  gas  by  the  application  of  acids. 

(c)  The  "mild  alkalies"  on  treatment  with  lime  became   "caustic," 

and  at  the  same  time  chalk  was  formed  in  the  proportion  of 
chalk :  lime,  as  had  been  found  in  the  reverse  direction  in  experi- 
ment (a). 

These  results  led  him  to  the  modern  interpretation  of  the 
relations  subsisting  between  lime  and  chalk,  magnesia,  and 
magnesium  carbonate,  and  the  "caustic"  and  "mild"  alkalies. 

The  following  description  of  the  discovery  of  the  more  no- 
table metallic  oxides  and  salts  may,  although  not  exhaustive,  be 
of  interest : — 

The  Ancients  were  acquainted  with  soda  and  potash,  lime  and  magnesia, 
and  the  corresponding  carbonates  ;  iwith  rock  salt,  saltpetre,  copper, 
vitriol,  alum,  cassiterite  (SnO2)  and  others  of  the  more  plentifully  occurring 
minerals.  Naturally,  however,  there  was  little  or  no  distinction  drawn 
between  closely  allied  bodies  such  as  soda  and  potash  or  limestone  and 
magnesite  ;  magnesia,  alum,  and  lime  were  not  definitely  distinguished  by 
the  alchemists  or  iatro-chemists,  and  it  was  not  until  Scheele's  time  that 
baryta  ceased  to  be  regarded  as  a  casual  variety  of  lime. 

As  might  be  expected  from  the  development  of  experimental  research 
during  the  alchemical  era,  a  great  many  artificial  preparations,  as  well  as 
numerous  naturally  occurring  compounds,  were  discovered  by  the  metal- 
transmuters  and  their  successors,  the  iatro-chemists.  To  the  first  alchemical 
period  belong  the  discoveries  of  ammonium  chloride  (salmiac,  Geber), 
carbonates  (from  urine ;  and,  by  Basil  Valentine,  from  salmiac  and  potashes), 


NOTES  ON  THE  HISTORY  OF  ELEMENTS     65 

copper  oxides,  acetate  (verdigris),  and  sulphate  (preparations  by  van 
Helmont  and  Glauber),  silver  nitrate  (lunar  caustic),  gold  chloride  (from 
aqua  regia  and  gold) ;  of  calcium  sulphate  (gypsum,  etc.),  mercuric  oxide 
(Geber),  mercurous  chloride  (calomel,  Geber,  improved  later  by  Croll),  cor- 
rosive sublimate  (Geber) ;  of  the  various  alums  (Basil  Valentine ;  all  these 
were  much  confused  with  each  other  and  with  iron  vitriol,  FeSO4),  lead 
oxides  (litharge  and  minium),  sulphide,  and  carbonate  (white  lead,  with 
which  various  salts  of  zinc  were  confounded).  The  oxides  and  acids  of 
arsenic  were  known  to  Geber  and  Albertus  Magnus,  and  Basil  Valentine 
investigated  numerous  compounds  of  antimony  and  of  iron. 

The  iatro-chemists  were  responsible  for  the  investigation  of  sodium 
sulphate  (sal  mirabilis,  Glauber,  1658) ;  zinc  oxide  (Libavius),  chloride 
(as  an  oil,  Glauber),  sulphide  (Agricola)  and  sulphate  (vitriol),  distinguish- 
ing these  from  the  similar  lead  compounds ;  mercuric  sulphate  (turpeth, 
Paracelsus) ;  stannic  chloride  (spiritus  fumans  Libavii,  Libavius),  lead  and 
ferric  chlorides  (Glauber),  and  the  lead  acetates  (Libavius). 

During  the  phlogistic  period  a  considerable  amount  of  the  confusion 
between  similar  compounds  such  as  potassium  and  sodium  sulphates  or 
lime,  magnesia,  baryta  and  alum  was  removed,  and  a  clearer  knowledge 
of  the  following  amongst  many  other  substances  resulted ;  the  sulphates 
of  potassium,  magnesium  (Crew,  1695),  aluminium  and  iron ;  calcium 
chloride  and  nitrate ;  strontium  carbonate  (strontianite,  Crawford,  1790) ; 
the  various  oxides  of  manganese  (Scheele,  and  much  later,  in  the 
nineteenth  century,  Liebig  and  Wohler,  Mitscherlich  and  Franke)  and  of 
iron  (Proust,  and  comparatively  recently,  Fremy  on  ferrates). 

We  thus  arrive  at  the  modern  epoch  of  inorganic  chemistry,  in  which 
a  most  prominent  part  was  played  by  Berzelius  and  his  students.  These 
very  thoroughly  investigated,  from  about  1820  onwards,  the  compounds 
of  titanium,  zirconium,  thorium,  chromium,  molybdenum,  tungsten, 
uranium,  and  other  then  recently  discovered  metals ;  Roscoe  also  added 
to  the  knowledge  of  the  halides  of  tungsten,  while  its  complex  oxy-acids 
received  attention  from  Margueritte,  Marignac  and  6thers.  We  may 
also  mention,  amongst  a  mass  of  other  work,  the  researches  on  copper 
sub-oxides  (Rose  and  The"nard),  on  silver  sub-  and  per-oxides  (Wtfhler), 
and  on  the  complex  ammonia-metallic  salts  of  cobalt  (Rose,  Fremy, 
Jb'rgensen,  and  latterly  Werner),  chromium  (Christensen,  Pfeiffer), 
rhodium  (Jorgensen),  iridium  (Leidie)  and  platinum  (Magnus,  Jorgensen). 

§  3.  Mineralogy — Our  historical  survey  of  inorganic  com- 
pounds would  be  incomplete  without  reference  to  the  study  of 
naturally  occurring  bodies  as  distinct  from  those  manufactured 
in  the  laboratory.     Of  course  in  olden  times  the  overwhelming 
5 


66          A  SHORT  HISTORY  OF  CHEMISTRY 

bulk  of  substances  known  were  minerals  (limestone,  marble, 
rock  salt,  etc.),  since  experiment  played  such  a  minor  part  in 
the  chemistry  of  the  ancients.  Various  ores  and  precious  stones 
became  known  as  time  went  on,  and  when,  at  the  close  of 
the  phlogiston  era,  the  importance  of  gravimetric  analysis  was 
realized,  several  chemists  of  note  found  scope  for  their  energies 
in  laborious  but  necessary  analyses  of  the  minerals  then  known. 
Bergman,  Scheele,  Klaproth,  Fourcroy,  and  Vauquelin  gave 
especial  assistance  in  this  field,  their  researches  showing  that 
minerals  obeyed  the  same  laws  of  constant  and  multiple  propor- 
tions as  synthetic  compounds.  At  this  time,  too,  efforts  were 
made  to  classify  minerals,  but  chiefly  according  to  their  physical 
properties,  their  chemical  relations  being  almost  neglected.  The 
most  noteworthy  of  these  earlier  mineral  systems  were  those  due 
to  Werner  and  to  Ha'uy  of  Paris,  towards  the  end  of  the  eigh- 
teenth century.  The  latter  based  his  classification  chiefly  on 
similarity  in  crystal  form  (cf.  "  Crystallography,"  chap.  x.). 

Bergman,  on  the  other  hand,  emphasized  the  importance  of 
the  chemical  composition  of  minerals,  although  in  his  day  so 
little  was  known  of  this  side  of  the  question. 

The  most  thorough  classification  of  minerals,  however,  was 
due  to  Berzelius,  who  in  1812  showed  that  their  composition 
was  in  entire  agreement  with  Dalton's  atomic  theory,  and  that 
they  were  inorganic  compounds  of  exactly  the  same  order  as 
any  prepared  in  the  laboratory.  In  1824  he  produced  a  mineral 
system,  based  on  the  dualistic  hypothesis,  dividing  minerals  into 
non-oxidized  and  oxidized  compounds.  Although  various  modi- 
fied classifications  have  since  appeared  from  time  to  time,  these 
present  no  fundamental  difference  from  that  of  Berzelius. 

The  nomenclature  of  minerals  has  never  been  properly  sys- 
tematized, for  they  are  still  named  according  to  individual 
peculiarity,  or  to  the  locality  where  first  found,  or  in  order  to 
perpetuate  the  names  of  their  discoverer  or  his  friends,  but 
rarely  so  as  to  show  somewhat  of  their  chemical  composition. 

During  the  past  100  years  mineralogy  has  been  characterized 


NOTES  ON  THE  HISTORY  OF  ELEMENTS     67 

by  attempts  to  synthesize  minerals  (a  kind  of  chemical  geology) 
and  by  the  systematic  investigation  of  newly  discovered  ones. 

Amongst  the  synthetic  efforts  must  be  mentioned  the  con- 
version of  chalk  to  marble  (Hall,  1 80 1),  the  artificial  preparation 
of  arragonite  (G.  Rose),  Bunsen's  researches  on  the  geysers  of 
Iceland,  Van't  Hoff's  studies  with  reference  to  ocean  deposits, 
and,  finally,  the  comprehensive  work  of  a  school  of  French 
chemists,  represented  by  Senarmont,  Levy,  Friedel,  Berthelot, 
and  Moissan.  These  have  reproduced  in  the  laboratory  the 
formation  of  quartz,  etc.,  by  slow  double  decomposition  in 
solution ;  the  slow  crystallization  of  dilute  solutions  (gypsum, 
etc.)  ;  the  action  of  water  under  high  pressure  at  varying  tem- 
peratures ;  and  the  formation  of  minerals  in  the  interior  of  the 
earth  or  in  prehistoric  times  by  the  action  of  intense  heat,  with 
or  without  an  accompanying  enormous  pressure  (Berthelot, 
Moissan) ;  the  preparation  of  carbides,  nitrides,  etc.,  in  the 
electric  furnace,  the  interchange  of  allotropic  forms  of  the 
elements  (e.g.  production  of  small  diamonds,  etc.  etc.). 

New  minerals  have  been  found  both  as  the  result  of  geo- 
graphical exploration  and  of  more  thorough  examination  of 
previously  known  deposits.  '  Examples  in  the  first  category  may 
be  taken  from  the  discovery  of  platinum  and  allied  ores  in 
South  America,  of  new  ores  (along  with  tin  and  other  known 
metals)  in  Borneo,  of  gold  in  various  continents  (Africa,  Aus- 
tralasia, North  America),  and  (recently)  of  numerous  rich  de- 
posits of  silver,  cobalt,  and  many  other  metals  in  Northern 
Canada. 

Berzelius  and  his  co-workers  discovered  many  ores  containing 
chromium,  molybdenum,  vanadium,  and  allied  metals;  Mosander 
in  1841,  and  many  workers  since,  have  investigated  the  ores  of 
yttria,  gadolinite,  etc.,  occurring  chiefly  in  Scandinavia .  and 
Greenland.  About  fifty  years  ago  the  deposits  of  soluble  salts 
at  Stassfurt  (near  Magdeburg)  were  discovered,  and  have  been 
extensively  utilized  in  many  ways  (manures,  preparation  of 
magnesium,  potassium,  etc.) ;  they  consist  mainly  of  chlorides 


6S  A  SHORT  HISTORY  OF  CHEMISTRY 

and  sulphates  of  potassium,  magnesium,  sodium,  and  calcium. 
Of  late  years  a  notable  class  of  minerals  has  been  studied,  viz. 
those  containing  occluded  gases,  usually  hydrogen,  nitrogen, 
carbon  dioxide,  helium,  and  sometimes  argon  and  neon-(cleveite, 
malacone,  gadolinite,  etc.).  The  chemical  examination  of 
meteorites  must  not  be  forgotten,  since  this  has  confirmed  the 
spectroscopic  evidence  that  extra-terrestrial  bodies  are  for  the 
most  part  made  up  of  the  same  elements  as  our  own  planet 
(Wohler,  Wolcott  Gibbs). 

§  4.  The  Chemical  ^Elements — The  preceding  paragraphs 
will  have  shown  clearly  that  in  the  majority  of  cases  the  dis- 
covery of  an  element  was  long  preceded  by  a  knowledge  of  its 
compounds,  and  that,  further,  the  presence  of  a  previously 
overlooked  element  has  often  been  realized  a  considerable  time 
before  chemical  methods  were  sufficiently  advanced  for  its 
isolation  (e.g.  sodium,  calcium,  lithium,  vanadium,  fluorine, 
etc.).  On  pp.  69,  70,  we  give  a  table  of  the  elements  (grouped 
according  to  the  periodic  system)  showing  the  circumstances 
of  their  discovery,  and,  when  not  isolated  by  their  discoverer,  of 
their  isolation. 

A  few  isolated  points  in  the  history  of  inorganic  compounds 
remain  to  be  dealt  with.  The  existence  of  different  forms  of 
the  same  substance  (e.g.  charcoal,  graphite,  diamond)  has  been 
investigated  by  imany  workers  since  Berzelius  characterized 
such  phenomena  as  a  particular  form  of  isomerism.  The  term 
"allotropy"  was  introduced  about  1841.  It  has  latterly  been 
realized  that  such  inorganic  isomers  are  probably  caused  by 
polymerism  (difference  in  molecular  weight)  or  polymorphism 
(difference  in  crystalline  form,  probably  due  to  difference  in 
molecular  structure).  Besides  oxygen  and  ozone  (Schonbein, 
1840),  the  following  cases  of  elementary  allotropy  have  been 
studied  :  sulphur  (Mitscherlich,  1852),  selenium  (Berzelius,  1817; 
Hittorff,  1851),  boron  and  silicon  (Wohler),  tin  (Rammelsberg, 
1880).  There  are  probably  more  cases  of  allotropy  in  the 
realm  of  compounds  than  of  elements,  but  comparatively  few  of 


NOTES  ON  THE  HISTORY  OF  ELEMENTS     69 


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A  SHORT  HISTORY  OF  CHEMISTRY 


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NOTES  ON  THE  HISTORY  OF  ELEMENTS      71 

these   (e.g.  the  iodides  and  sulphides  of  mercury)  have  been 
minutely  studied. 

The  hydrides  of  the  elements  form  an  interesting  series ; 
those  of  the  alkaline  and  alkaline  earth  metals  are  of  compara- 
tively recent  discovery,  the  rest  are  mainly  non- metallic.  The 
most  noteworthy  are  those  of  boron  (B3H3,  Ramsay  and  Hat- 
field),  silicon  (SiH4,  Wohler,  1857  ;  Si2H6,  Moissan  and  Smiles, 
1902),  sulphur  (H2S,  Rouelle ;  H2S2,  Scheele),  and  the  nitrogen 
group,  which  merit  special  attention  : — 


SfH3 


NH(OH)2 
N2H4 

N3H 


AsH3 
SbH, 


Ammonia  Compounds  known  to  the  ancients ; 

gas  discovered  by  Priestley,  1774. 
Discovered  by  Lessen,  1865 ;  obtained 
pure  by  Lobry  de  Bruyn  and  by 
Crismer,    1891;    sulphonic  acids 
studied  by  Lossen,  Divers,  etc. 
In  solution  only  ;  Angeli,  1907. 
Discovered  by  Curtius,i887 ;  obtained 

pure  by  Lobry  de  Bruyn,  1896. 
Discovered  by   Curtius,  1890;    also 
obtained  by  W.  Wislicenus,  1892. 

Gaseous  phosphoretted  hydrogen  Discovered  by  Gengembre,  1783. 
Liquid  phosphoretted  hydrogen  „  The"nard,  1845. 

Arsine  ,,  Scheele. 

Stibine  „  Soubeiran,  1830. 


Hydroxylamine 


Dioxyammonia 
Hydrazine 

Hydrazoic  acid,  azo-imide 


The   oxides  and    oxy-acids  of    nitrogen,   phosphorus   and 
sulphur  are  worthy  of  note  : — 


N20  Nitrous  oxide 

N20.jH.2  Hyponitrous  acid 

NO  Nitric  oxide 

N2O:;  Nitrogen  trioxide 
N0.2  ,,        peroxide 

N^O-,  ,,        pentoxide 

H3P(X  Phosphorous  acid 

H4P2Or,  Hypophosphorous  acid 

SO3  Sulphur  trioxide 

SaO,  Sulphur  sesquioxide 


Davy,  1806  ("  laughing  gas  "). 
Divers,  1871 ;  ThieleandLachmann, 

1895 ;  Hantzsch,  1896. 
Priestley,  Dulong,  Pe*ligot. 
Dulong,  1816;  Peligot,  1841. 
Dulong,  Gay-Lussac. 
St.  Clare  Deville,  1849. 
Lavoisier ;  Wurtz,  1849. 
Salts  by  Dulong,  1816. 
Isolated  by  Dobereiner. 
„  Weber,  1864. 


A  SHORT  HISTORY  OF  CHEMISTRY 


H2SaO3  Thiosulphuric  acid 

H2S(n)O6        Polythionic  acids  (n  =  2  to  5) 
Hyposulphurous  acid 


Salts  by  Gay-Lussac,  1819  ("hypo- 
sulphurous  acid  "). 

Investigated  since  1840  by  Wacken- 
roder,  Spring,  etc. 

H2SO2,       Schutzenberger,       1869  ; 
H2S2O4,        Bernthsen,         1900 
H4S2O5,  Bucherer,  1904. 


There  are  also  several  substances  of  interest  related  to  hydro- 
gen peroxide : — 

O3  Ozone  Discovered  by  Schonbein  (1840) ;  con- 

stitution by  Marignac,  Andrews 
and  Soret ;  much  used  of  late  in 
organic  chemistry  as  oxidizing 
agent. 

Discovered  by  ThSnard  (1818) ;  an- 
hydrous, Wolffenstein  (1894). 

Isolated  by  Berthelot,  1878  (SO2  +  O2 
under  silent  discharge). 

Only  known  in  dilute  solution ; 
K2S2O8,  electrolysis  of  KHSO4 
(Marshall,  1891). 

Isolated  by  H.  Caro  (1898) ;  used  by 
Baeyer  as  organic  oxidant ; 
H4S2O9,  Armstrong  and  Lowry, 
1902. 

Obtained  by  electrolysis  of  MHCO3 
(Constan  and  Hansen,  1897). 

H2O2  on  chromic  acid  solution 
(Barreswil,  1847;  Moissan,  Ber- 
thelot) ;  boric,  molybdic,  tungstic 
and  uranic  acid  salts  all  yield 
peracids  with  H2O2. 

Finally,  there  are  a  number  of  halides  of  the  elements  whose 
discovery  presents  points  of  interest : — 


H2O2  Hydrogen  peroxide 

S2O7  Persulphuric  anhydride 

H2SaOg  Di-persulphuric  acid 

H2S05  Mono-persulphuric  acid 

M^CaOg          Percarbonates 
KCrO5,H2O2  Potassium  perchromate 


BX3 
SiX4 


Boron  halides  \ 
Silicon  halides  } 
Nitrogen  chlorides 

Nitrogen  iodides 


Investigated    mainly    by    Berzelius, 

Wohler  and  Deville. 
First  studied  by  Dulong  (1812)  and 
then  Gattermann. 
,,  Gay-Lussac. 


NOTES  ON  THE  HISTORY  OF  ELEMENTS    73 


Phosphorus  trichloride  First  studied  by  Gay-Lussac  (1800). 
^Clg                         „          pentachloride  „  Davy  (1800). 

'OClg  ,,  oxychloride  ,,  Wurtz  (1847). 

JF5  ,,          pentafluoride  „  Thorpe  (1876). 

\.sCls  Arsenic  trichloride  „  Glauber. 

§  5.  The  Metals  of  the  Rare  Earths — There  are  a 
number  of  rare  metals,  for  the  most  part  occurring  together  in 
a  few  rare  minerals  of  not  very  wide  distribution  (chiefly  in 
Scandinavia  and  Canada),  and  these  are  characterized  by  great 
similarity  in  chemical,  and  in  many  physical,  properties.  In 
some  cases  chemical  reactions  do  not  suffice  to  effect  their 
separation,  which  can  only  be  accomplished  by  fractional 
crystallization  of  their  salts,  the  process  being  controlled  by 
spectroscopic  examination. 

The  following  is  a  list  of  these  elements,  taken  from  the 
International  Atomic  Weight  table  for  1909  : — 

Element.  At.  Wt.                           Discovery. 

Scandium  44-1  1879  Nilson. 

Yttrium  89-0  1794  Gadolin. 

Lanthanum  139-0  1839  Mosander. 

Cerium  140-25  1803  Klaproth. 

Praseodymium  140-6 )  f  1841  Mosander  (Didymium). 

Neodymium  I44'3-'  1 1885  Resolved  by  Welsbach. 

Samarium  *5°'4  l849  Lecoq  de  Boisbaudran. 

Europium  152-0  1896  Demarcay. 

Gadolinium  157-3  l889  Lecoq  de  Boisbaudran. 

Terbium  159-2  1843  Mosander. 

Dysprosium  162-5  l886  Lecoq  de  Boisbaudran. 

Erbium  167*4  J843  Mosander. 

Thulium  168-5  l877  Cleve ;  1906  Urbain. 

Ytterbium  172-0  1878  Marignac. 

Lutecium  I74*°  I9°7  Urbain. 

As  previously  remarked,  this  series  is  of  great  theoretical 
interest,  since,  as  Crookes  has  shown  (1885-9,  etc.),  it  appears 
to  comprise  a  number  of  elements  which  are  far  more  intimately 
related  to  each  other  ("  meta-elements,"  1889)  than  is  commonly 
the  case,  and  may  therefore  throw  some  more  light  on  the 


74  A  SHORT  HISTORY  OF  CHEMISTRY 

problem  of  the  genesis  of  the  elements.  In  the  meantime  it 
must  be  pointed  out  that  scandium,  yttrium,  lanthanum  and 
perhaps  cerium  are  the  only  members  of  the  group  which 
readily  fall  into  line  with  the  periodic  system ;  in  connexion 
with  this  Benedicks  (1904)  has  suggested  that  the  metals  with 
atomic  weights  intermediate  between  those  of  barium  and  tan- 
talum be  interposed  as  a  kind  of  transitional  series  between 
these  two.  It  is  noteworthy  that  this  scheme  tends  to  consoli- 
date the  periodic  table,  leaving  only  eight  vacant  spaces. 

§  6.  Radio-active  Elements — Since  the  science  of  radio- 
activity came  into  being  search  has  naturally  been  made  for 
the  elements  which  give  rise  most  markedly  to  the  phenomenon, 
and  at  the  present  time  five  such  elements,  all  of  them  of  very 
high  atomic  weight,  are  certainly  known,  viz.  uranium,  thorium, 
radium,  polonium  and  actinium.  In  1896  Becquerel  noticed 
the  radio-activity  of  uranium,  and  six  or  seven  years  later 
Madame  Curie  observed  that  of  thorium,  and  also  stated  that 
it  was  only  the  product  from  natural  sources  (pitch-blende) 
which  showed  very  marked  activity,  the  effect  being  much 
stronger  than  any  observed  with  pure  laboratory  uranium  or 
thorium  compounds.  On  the  other  hand,  the  latter  showed 
about  one  hundred  times  as  much  radio-activity  as  any  com- 
pound of  other  elements,  and  it  was  held  to  be  doubtful 
whether  any  other  element  was  at  all  radio-active. 

Mme.  Curie,  therefore,  fractionally  analyzed  pitch-blende  in 
an  attempt  to  isolate  the  more  radio-active  constituents,  and 
found  that  the  radio-activity  became  concentrated  in  the 
barium  and  bismuth  groups.  She  fractionated  the  chlorides 
from  the  barium  precipitates,  and  finally  obtained  OT  gm.  pure 
radium  chloride  from  a  ton  of  pitch-blende.  Giesel  improved 
the  method  of  fractionation  by  using  the  bromides  instead  of 
the  chlorides,  and  so  obtained  0-25  gm.  pure  salt  from  a  ton  of 
mineral.  Mme.  Curie  determined  the  atomic  weight  of  radium 
by  precipitating  the  chloride  with  silver  nitrate,  and  obtained 
the  value  225,  agreeing  with  the  place  assigned  to  radium  in  the 


NOTES  ON  THE  HISTORY  OF  ELEMENTS      75 

periodic  system.  Runge  and  Precht  estimated  the  atomic 
weight  later  as  257*8,  from  spectroscopic  calculations,  but 
Mme.  Curie's  value  has  been  confirmed  (1908)  by  Haitinger 
and  Ulrich,  working  with  larger  quantities  of  radium  bromide. 

Mme.  Curie  and  Debierne  have  very  recently  isolated  radium 
as  a  white,  easily  oxidized  metal  by  electrolysis  of  the  fused 
salts,  using  a  mercury  cathode. 

Mme.  Curie  next  worked  up  the  precipitates  of  the  bismuth 
group,  and  discovered  a  new  element,  polonium^  but  did  not 
succeed  in  isolating  a  pure  salt.  Marckwald  (1903),  however, 
prepared  the  element  in  a  state  of  purity,  but  only  obtained 
4  milligrams  from  two  tons  of  pitch-blende.  Polonium  was 
found  to  resemble  tellurium. 

Finally,  Giesel  (1902)  and  Debierne  (1903)  discovered  an 
element,  similar  to  thorium  or  titanium,  but  more  radio-active, 
which  has  been  named  actinium. 


CHAPTER  VI 
THE  HISTORY  OF  ORGANIC  CHEMISTRY 

§  i.  Organic  Chemistry:  the  Chemistry  of  Animate 
Nature — The  knowledge  of  the  laws  governing  the  combina- 
tion of  the  chemical  elements  and  the  views  held  at  the  present 
day  with  respect  to  the  final  constitution  of  matter  have  been 
mainly  derived  from  inorganic  or  mineral  substances,  while  the 
theories  of  how  the  atoms  are  linked  together  in  a  compound 
are  based  upon  what  has  been  discovered  during  the  past  cen- 
tury with  reference  to  organic  substances,  or,  in  the  nomencla- 
ture of  Lavoisier's  time,  bodies  of  animal  or  vegetable  origin. 
Many  simple  organic  compounds  had  of  course  been  met  with 
very  early  in  chemical  history ;  marsh  gas  was  known  to  van 
Helmont,  alcohol  (or,  aqua  vitae,  as  the  alchemists  thought 
best  to  call  it),  ether  and  several  of  the  simpler  ethyl  esters  (e.g. 
"  sweet  spirits  of  nitre ")  were  prepared  and  used  medicinally 
and  otherwise  much  before  his  time,  while  quite  a  number  of 
organic  acids  (such  as  acetic,  oxalic,  benzoic)  were  known  to  the 
alchemists  or  phlogistonists,  and  to  these  Scheele  added  several 
more,  discovered  by  him  in  various  plant  or  animal  juices  (malic, 
citric,  oxalic,  prussic,  tartaric,  lactic,  uric  acids).  All  organic 
compounds  known  at  the  beginning  of  the  nineteenth  century 
were  in  fact  directly  obtained  from  animate  nature,  and  of  the 
more  complicated  substances  a  few  sugars  and  plant  bases  were 
practically  all  that  were  known. 

Difficulty  was  found  in  accommodating  the  simple  dualistic 
hypotheses  of  Lavoisier,  Davy,  etc.,  to  the  cases  of  such  organic 

76 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      77 

compounds,  and  many  thought  that  these  were  part  of  a  distinct 
realm  of  chemical  nature,  subject  to  different  laws.  This  and 
the  source  of  all  the  organic  substances  then  known  together 
led  to  the  idea  that  such  bodies  were  only  formed  by  the 
intervention  of  a  special  "  vital  force  ".  This  view,  which  was 
also  suggested  by  various  workers,  notably  Bergman,  in  the 
previous  (phlogistic)  period,  was  rendered  untenable  when  it 
was  shown  that  in  several  instances  pairs  of  substances  of  the 
same  empirical  composition — one  recognized  as  "  inorganic  " 
and  the  other  as  "  organic  "  (the  terms  bearing  at  that  time  their 
literal  meaning) — were  so  closely  related  that  one  member 
could  frequently  be  changed  into  the  other. 

The  discovery  of  isomerism,  indeed,  marks  the  commence- 
ment of  our  modern  structural  chemistry,  and  at  this  point  the 
detailed  description  of  its  history  must  begin. 

In  1825  Faraday  discovered  a  hydrocarbon,  butylene,  of 
the  same  percentage  composition  as  Dalton's  defiant  gas,  and 
shrewdly  predicted  that  more  instances  of  the  kind  would  fol- 
low in  connexion  with  carbon  compounds.  Somewhat  earlier 
(1823)  Liebig  and  Wohler  proved  the  existence  of  two  isomeric 
acids,  cyanic  and  fulminic  acids,  and  in  1828  the  latter  dis- 
covered the  famous  conversion  of  ammonium  cyanate  to  urea. 
Again,  in  1832,  Liebig  and  Mitscherlich  showed  that  Berzelius' 
sarcolactic  acid  from  flesh  (1807),  and  Scheele's  lactic  acid 
from  sour  milk  (1780)  possessed  the  same  composition,  and 
at  about  the  same  time  Berzelius  isolated  racemic  acid,  of  the 
same  composition  as  Scheele's  tartaric  acid  from  argol. 

In  1831  Berzelius  proposed  the  term  "isomerism"  and  a 
year  later  subdivided  it  into  two  new  ones,  "  polymerism  "  and 
"  metamerism,"  which  in  the  course  of  time  became  changed 
to  "polymerism"  (substances  of  the  same  empirical  but  dif- 
ferent molecular  composition),  and  "isomerism"  (different 
substances  of  the  same  molecular  composition). 

§  2.  The  Earlier  Theories  of  Structure  of  Organic 
Compounds — To  understand  the  transition  from  this  early 


78  A  SHORT  HISTORY  OF  CHEMISTRY 

and  somewhat  chaotic  state  of  affairs  to  the  present  tolerably 
well-ordered  system  of  organic  theory,  we  have  to  glance  at  a 
complicated  series  of  hypotheses  designed  in  succession  to 
explain  organic  reactions.  These  may  be  roughly  grouped  as 
follows  : — 

(1)  "  Radicle  "  theories. 

(2)  "  Type  "  theories. 

(3)  The  modern  structural  theory,  which  in  some  measure 
combines  both  the  preceding. 

Since  these  temporary  hypotheses  were  devised  contem- 
poraneously with  the  various  systems  of  atomic  weights  des- 
cribed in  Chapter  iii.  the  formulae  used  by  their  authors  are  very 
confusing,  and  so  as  far  as  possible  the  corresponding  modern 
formulas  are  added  in  brackets  in  the  resume  of  their  work 
which  follows : — 

(i)  "RADICLE"  THEORIES. 

Lavoisier's  extension  of  his  oxygen  theory  to  include  organic 
acids  has  already  been  mentioned ;  he  seems  to  regard  these 
as  oxides  of  "  radicles "  containing  more  than  one  element, 
and  including  in  any  case  carbon  and  hydrogen.  A  more 
precise  view  of  .a  "  compound  radicle  "  was  arrived  at  by  Gay- 
Lussac  (1815-22)  as  the  result  of  his  work  on  the  cyanogen 
compounds,  from  which  it  was  clear  that  the  cyanogen  group 
functioned  as  a  "  compound  element "  by  forming  a  whole 
series  of  compounds,  such  as  cyanogen  hydride  (HCN),  chlo- 
ride, bromide,  iodide,  etc.  Further  support  was  given  to  the 
view  that  organic  chemistry  is  the  "  chemistry  of  compound  ra- 
dicles "  by  Liebig  and  Wohler's  investigation  of  the  "  radicle  of 
benzoic  acid"  in  1832.  They  prepared  benzoyl  hydride  (benz- 
aldehyde),  hydrate  (the  acid),  halides,  sulphide,  ether  and  other 
compounds,  thus  showing  that  "benzoyl"  CHH10O2(C7H5O) 
behaved  in  analogous  fashion  to  a  simple  element.  Berzelius 
strongly  supported  this  first  radicle  theory^  since  it  con- 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      79 

firmed  his  own  dualistic  electrical  hypothesis  by  extending 
it  to  organic  substances.  Several  other  radicles  were  inves- 
tigated in  succeeding  years,  notably  cinnamyl  (1834,  Dumas 
and  Peligot),  salicyl  (1838,  Piria),  and  cacodyl  (1837-43, 
Bunsen),  and  the  simple  theory  of  organic  radicles  was  generally 
accepted  between  the  years  1837-40. 

Other  observations  of  Gay-Lussac  (upon  the  relations  be- 
tween ethylene,  alcohol  and  ether)  led  to  Dumas  and  Boullay's 
etfierin  theory.  These  authors  tried  to  show  in  1828  that 
ethylene  (etherin)  performed  similar  functions  to  ammonia  as  a 
compound  radicle,  in  order  to  explain  (on  a  "  radicle  "  basis)  the 
connexion  between  alcohol,  ether,  and  allied  compounds ;  they 
pushed  the  analogy  too  far,  however,  by  suggesting  that  ethylene 
was  essentially  a  base  like  ammonia,  and  this  brought  more 
discredit  than  was  perhaps  fair  to  the  original  hypothesis,  which 
looked  upon  alcohol,  ether,  and  ethyl  chloride,  for  instance,  as 
the  respective  hydrate,  oxide,  and  hydro-chloride  of  etherin. 

In  1834  Liebig  and  Berzelius  parted  company  to  a  certain 
extent  with  respect  to  their  views  on  organic  structure.  Berzelius 
was  always  tied  down  by  his  dualistic  theory,  which  he  seems 
to  have  placed  before  all  other  considerations.  He  insisted  on 
regarding  all  oxygenated  compounds  as  oxides,  and  so  assumed 
that  ether  and  alcohol  were  oxides  of  two  different  radicles 
(C2H5)2  and  C2HG.  Liebig  on  the  contrary  held  that  these 
were  derivatives  of  the  same  radicle  "  ethyl,"  but  ascribed  to 
"  ethyl "  double  its  real  molecular  weight,  whereas  Berzelius  was 
correct  in  this  point,  as  will  be  seen  from  the  following  table  : — 

Modern.  Liebig,  1834.  Berzelius,  1833. 

Alcohol  C2H6O       Ethyl  oxide  hydrate  C4H10O  .  H2O     (C2H6)O 
Ether  C4H10O        Ethyl  oxide  C4H10O  Ethyl  sub-oxide  (C3H-)2O 

Finally,  in  1838,  Liebig  tried  to  modify  still  further  the  con- 
ception of  the  structure  of  alcohol  by  taking  what  he  called 
the  "  acetyl "  radicle  C4H6(CH3C — )  as  his  basis.  A  little  con- 
sideration will  show  how  this  dehydrogenation  of  the  ethyl 


8o  A  SHORT  HISTORY  OF  CHEMISTRY 

group  permitted  of  the  oxidation  products  of  alcohol,  aldehyde, 
and  acetic  acid,  being  classed  as  derivatives  of  the  same  group 
as  that  present  in  alcohol  and  ether. 

We  may  therefore  sum  up  the  period  of  "  radicle  theories  " 
as  :  (a)  a  general  adherence  to  the  view  that  organic  bodies 
are  composed  of  radicles  (groups  of  atoms)  which  function  as 
elements  and  which  are  in  general  preserved  intact  through  a 
whole  series  of  reactions ;  (b)  a  series  of  efforts  to  bring  the 
simple  compounds  such  as  alcohol,  ether,  acetic  acid  and  the 
like  into  line  with  the  more  distinctive  and  well-defined  radicles 
such  as  benzoyl,  cacodyl  and  cyanogen. 

(2)  "  TYPE  "  THEORIES. 

The  fact  which  above  all  others  tended  to  throw  doubt  upon 
the  radicle  theories  was  the  substitution  of  hydrogen  by  chlor- 
ine in  organic  compounds.  This  phenomenon,  which  was 
impossible  according  to  the  upholders  of  the  dualistic  view, 
was  observed  by  Gay-Lussac,  Liebig  and  Wohler,  Faraday,  and 
Dumas  in  the  respective  cases  of  hydrocyanic  acid,  benzaldehyde, 
ethylene  and  alcohol  (to  chloral),  and  in  1834  the  last-named 
worker  summed  up  the  facts  in  his  Laws  of  Substitution  (or 
metalepsy,  to  use  his  own  term).  In  1837  Laurent  made  an 
attempt,  to  some  extent  temporarily  successful,  to  reconcile  the 
radicle  theories  with  the  new  substitution  laws  by  suggesting 
that  the  radicles  could  be  altered  to  a  certain  degree  by  sub- 
stitution, but  that  there  always  remained  a  nucleus  (of  carbon 
and  hydrogen)  which  was  unalterable. 

This  satisfied  neither  Berzelius  nor  Dumas,  although  it  prob- 
ably approaches  the  modern  structure  theory  more  nearly  than 
the  views  adopted  by  either.  A  few  years  later,  in  1840,  Dumas 
published  a  new  theory  which  supplanted  the  dualistic  by  a 
unitary  view,  each  compound  being  regarded  as  a  complete 
whole  in  itself,  its  components  being  related  in  analogous 
fashion  to  the  worlds  of  a  planetary  system.  At  the  same  time 


THE  HISTORY  OF  ORGANIC  CHEMISTRY     81 

he  attempted  to  classify  compounds  from  their  reactions  ac- 
cording to  definite  "  mechanical  types"  (a  method  also  suggested 
by  Regnault),  and  further  asserted  that  substances  closely  re- 
lated in  properties  belonged  to  the  same  "  chemical  type"  gene- 
ral structural  similarity  without  necessarily  similar  properties 
being  the  criterion  of  inclusion  in  a  given  "  mechanical  type  ". 
An  illustration  will  make  this  clearer  :  — 


4 

Chloracetic  acid^C^A    jChemical  type. 


Thus  there  was  no  definite  view  held  with  regard  to  organic 
constitution  in  the  beginning  of  the  forties,  and  as  this  was  also  the 
period  (cf.  chap.  iii.  p.  37)  when  no  fixed  rule  had  been  adopted 
by  which  to  determine  the  true  relation  between  atomic  weight 
and  equivalent,  there  was  considerable  confusion  in  almost 
every  department  of  chemical  theory.  The  criticisms  of  two 
French  chemists,  Laurent  and  Gerhardt,  upon  this  point  almost 
remind  one  of  the  scathing  words  of  Kunkel  and  Boyle  with 
reference  to  the  charlatan  alchemists. 

Laurent  in  1843  precisely  defined  the  terms  atom,  mole- 
cule, and  equivalent,  by  means  of  a  more  rigid  application  of 
Avogadro's  rule  than  had  hitherto  been  made. 

Gerhardt  and  Laurent  together  made  it  their  work  to  develop 
the  unitary  view  of  organic  structure,  as  opposed  to  the  dualism 
of  Berzelius  and  many  of  the  German  chemists.  A  preliminary 
to  this  advance  was  Gerhardt  's  "  Theory  of  Residues"  propounded 
in  1839.  Any  organic  reaction  which  can  be  represented  as  a 
binary  one,  e.g.  — 

C2H3OC1  +  NH3=C2H3ONH2+  HC1, 

must,  in  order  to  satisfy  the  observed  differences  between 
ordinary  inorganic  double  decomposition  and  the  reactions  of 
carbon  compounds,  be  explained  theoretically  on  a  different 
basis  (for  the  sake  of  clearness  it  may  be  pointed  out  that  in  our 
time  the  characteristics  of  most  inorganic  double  transpositions 
6 


82  A  SHORT  HISTORY  OF  CHEMISTRY 

are  considered  to  be  due  to  the  presence  of  the  reacting  sub- 
stances in  the  form  of  ions,  the  two  classes  of  reactions  being 
thus  ionic  and  non-ionic).  Gerhardt's  explanation  was  that  in 
such  binary  reactions  the  inorganic  parts  of  the  molecules  inter- 
acted in  the  ordinary  way  and  the  residual  (organic)  parts  then 
joined  to  form  the  new  organic  substance.  A  substance  so 
formed  was  called  a  "copulated"  compound — formed  by  the 
linking  together  of  the  two  residues.  Thus 

C]iH3OCl    (Acetyl  chloride)  +  NHS  =  HC1  +  QH3O|  (Acetamide). 

He  next  availed  himself  of  the  results  furnished  by  Liebig 
and  Graham  respectively  on  polybasic  organic  and  inorganic 
acids,  and  his  efforts  to  explain  these  in  a  similar  manner  led,  in 
1 844,  after  Laurent's  all-important  threefold  definition  recalled 
above,  to  a  much  simplified  scheme  of  atomic  and  molecular 
formulas,  and  especially  to  the  first  systematic  classification  of 
organic  compounds,  carried  out  jointly  by  these  two  workers. 

It  is  interesting  to  recall  that  Gerhardt  defined  organic 
chemistry  as  the  "  chemistry  of  the  carbon  compounds  "  rather 
than  of  "  compound  radicles,"  and  that  he  pointed  out  the 
general  recurrence  of  homologous  series  (already  hinted  at  by 
Schiel  (1842)  for  alcohols  and  Dumas  for  acids),  and  the  existence 
of  isologous  series  (the  corresponding  compounds  of  similar 
chemical  nature  in  different  homologous  series,  e.g.  alcohol  and 
phenol,  propyl  alcohol  and  the  cresols)  and  of  heterologous  series 
(which  are  practically  the  same  as  Dumas'  "  mechanical  types  " 
(loc.  cit.)). 

The  next  definite  advance  was  the  evolution  of  four  general 
types  by  Gerhardt  in  1853,  based  fundamentally  upon 

Hi  J  Hi  Hi 

hydrogen    TT  [-,    hydrochloric    acid     p,  [-,   water    TT  [O,  and 

HI 

H 

ammonia  H  >K.     (A  fifth  type,  methane  ^  [C2(C  =  6),    was 

H'  Hj 

afterwards  added  by  Kekule.) 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      83 

The  events  of  the  intervening  nine  years  between  1844  and 
1853  contributed  a  great  deal  to  this  further  systematization, 
and  must  be  briefly  summarized. 

In  the  first  place,  Kolbe  and  Frankland  engaged  upon  a 
series  of  researches  in  order  to  modify  the  old  Berzelian  theory 
so  as  to  make  it  accord  with  all  the  new  facts  then  known. 
In  1845  Kolbe  had  prepared  trichlormethyl  sulphonic  acid 
CC13 .  SO3H,  and  the  corresponding  mono-  and  di-chloro^acids, 
so  that  a  series  of  sulphonic  acids  entirely  analogous  to  the  fatty 
acids  from  acetic  to  trichloracetic  was  formed,  and  in  1849 
Frankland  prepared  numerous  organo-metallic  derivatives  (from 
the  metals  and  alkyl  iodides)  which  (by  interaction  with  water) 
readily  yielded  substances  believed  at  that  time  to  be  the 
"  radicles  "  themselves ;  at  the  same  time  these  chemists  jointly 
investigated  the  saponification  of  nitriles  to  fatty  acids  and  the 
action  of  potassium  on  ethyl  cyanide  (yielding  ethane,  but  the 
product  was  not  recognized  owing  to  some  experimental  error). 
Finally,  in  1850  Kolbe  electrolyzed  the  salts  of  the  series  of  fatty 
acids  and  believed  he  had  isolated  the  radicles  of  the  acids  (in 
reality,  of  course,  the  products  were  hydrocarbons  formed  by 
union  of  two  radicles,  e.g. 


COOK        K 


^v^fvyrv.  rv.         /• »v 

COOK  -*  K  +  2C02  +  C2H6'' 

They  believed  they  had  thus  shown  : — 

(a)  the  importance  of  the  alkyl  radicles  in  determining  the 
character  of  a  compound  (e.g.  CH3~,  CH2C1-,  CHC12-, 
CC13-). 

(^)  the  existence  of  the  radicles  themselves. 

(c)  the  fatty  acids  to  be  "  copulated  compounds  "  l  of  oxalic 

1  Kolbe  and  Frankland  used  "  copulated  compound  "  in  the  sense  given 
to  the  term  by  Berzelius,  which  differed  from  that  in  which  it  was  used  by 
Gerhardt,  for  Berzelius  apparently  simply  meant  that  in  a  "copulated 
compound"  a  neutral  group  was  joined  to  an  electro-positive  or  negative 
group. 


84  A  SHORT  HISTORY  OF  CHEMISTRY 

H20 

acid  and  the  alkyl  radicles  (since  (CN),  --  >(COOH)2,  and 


R  .  CN—  ->R  .  COOH). 

Much  later,  in  1857,  Kolbe  suggested  that  carbonic  acid 
served  as  the  fundamental  type  of  organic  acid,  showed  how 
aldehyde,  alcohol,  and  hydrocarbon  types  could  be  derived 
therefrom,  and  proved  there  was  some  truth  in  his  view  by 
predicting  the  existence  and  properties  of  formaldehyde  and  of 
secondary  and  tertiary  alcohols,  then  unknown,  but  discovered 
soon  after  ;  e.g. 


aHO.(CA).Oa       HQ     .  (CA).  02        H.(CaOa),H         HO.C2H3,  O 
Carbonic  Acid  Formic  Acid  Formaldehyde        Methylalcohol 

(HO  .  CO  .  OH)          (H  .  CO  .  OH)  (H  .  CO  .  H)  (HO  .  CH,) 

On  the  other  hand,  much  experimental  work  was  accumulated 
during  this  decade  which  strengthened  the  "  theory  of  types  ". 
The  outstanding  features  are  :  — 

1849  Wurtz.  Formation  of  amine  bases  from  cyanic  esters  and 

ammonia. 

1850  Hofmann.        Formation   of  ammonium  or    aniline  bases  from 

alkyl  iodides  and  ammonia  or  aniline. 
(Cf.  1845,  The"nard's   preparation  of  analogous 

phosphine  bases.) 

1850-52  Williamson.     Preparation  of  ether  from  ethyl  iodide  and  potas- 
sium ethylate. 

The  last-mentioned  was  perhaps  the  most  important  of  all, 
for  it  demonstrated  that  ether  bore  the  same  relation  to  alcohol 
as  an  alkaline  oxide  to  its  hydroxide  (a  connexion  previously 
suggested  by  Laurent  in  1846). 

Williamson  was  thereby  enabled  on  a  similar  basis  to  explain 
the  much-discussed  mechanism  of  the  preparation  of  ether  from 
alcohol  and  sulphuric  acid  (previously  ascribed  by  Mitscherlich, 
Berzelius,  and  others,  in  default  of  anything  better,  to  "  catalytic 
action  "),  and  to  suggest  that  alcohols,  ethers,  acids,  and  their 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      85 
derivatives  all  belonged  to  one  and  the  same  "water  type" 

TT"| 

lO.     The  preparation  of  acid  anhydrides  from  acid  chlorides 
HJ 
and  fatty  acid  sodium  salts  by  Gerhardt,  in  1852,  came  as  an 

excellent  confirmation  of  this  theory. 

A  little  later  (1854)  Williamson  and  Kay  gave  a  further 
example  of  the  fruitfulness  of  this  "  type  "  hypothesis  by  syn- 
thesizing the  first  dibasic  alcohol  —  glycol,  from  ethylene  iodide  — 
its  existence  having  become  probable,  since  they  had  recently 
prepared  orthoformic  ester,  and  Berthelot  had  just  shown  gly- 
cerol  to  be  tri-basic,  these  being  the  first  instances  Q{  tri-basic 
alcohol  derivatives  known,  thus  leaving  a  gap  which  was  filled 
by  glycol. 

In  the  meantime  it  had  become  customary  to  refer  the 
ammonium  bases  of  Hofmann  and  Wurtz  to  the  "  ammonia 
type,"  and  Williamson  suggested  that  combinations  of  these, 
yielding  "  mixed  types,"  occurred  in  the  more  complicated  com- 
pounds. It  will  be  noticed  that  the  term  "  mixed  type  "  is 
more  or  less  synonymous  with  Gerhardt's  view  of  a  "  copulated 
compound  ".  For  example  :  — 


H 

Acetic  Acid  Ammonia,  Amidoacetic  Acid 

He  also  extended  the  idea  to  inorganic  acids  and  bases, 
though  not  with  such  great  success  as  on  the  organic  side. 

Kekule's  first  paper  in  connexion  with  organic  structure  (in 
1854)  dealt  with  the  extension  of  Gerhardt's  simpler  types  to  an 
extended  series  of  mixed  types. 

It  will  be  seen  that  Gerhardt's  generalization  was  a  combina- 
tion of  those  parts  of  the  older  radicle  and  type  theories  which 
had  survived  the  test  of  application  to  the  numerous  new  facts 
discovered  between  1830  and  1850,  and,  further,  that  the  next 
development  (the  idea  of  atomicity  or  valency)  was  a  very  gentle 
transition  from  the  four  main  types  :  — 


86  A  SHORT  HISTORY  OF  CHEMISTRY 


Hl 
a; 

H. 

It  will  be  useful  to  give  a  table  of  the  different  advances  made 
in  each  of  the  two  kinds  of  structure  theories  : — 

Radicle.  Type. 

1822  "  Cyanogen "  (Gay-Lussac).         1834  "Laws     of     Substitution" 
1832  "Benzoyl"       (Liebig      and  (Dumas). 

Wohler).  1837  Nucleus  theory  (Laurent). 

1832  The    older    radicle    theory         1840  Type  theory  (Dumas). 

(Liebig  and  Wohler,  Ber-         1839  Theory    of    Residues    (Ger- 

zelius).  hardt). 

1828  Etherin  theory  (Dumas). 
1834-8  New  radicle  theory  (ethyl 

andacetyl  theories,  Liebig). 


1844  Gerhardt  and  Laurent's  classification. 

1848-50  Evolution  of  ammonia  type  through  Wurtz's  and  Hofmann's  work. 

1850-2  Evolution  of  water  type  through  Williamson's  work. 

1853  Ger  hardt'  s  general  type  theory. 

1854-7  Williamson's  and  Kekule's  "  mixed  types  ". 

§  3.  Saturation  Capacity  and  the  Modern  Structure 

Theory  —  Kekule  saw  that  the  use  of  "  mixed  types,"  such  as 
|H 

N    H 

CO\       implied  the  presence   of  polybasic  radicles, 


and  in  1857  was  able  to  give  definitions  of  mono-  di-  and  tri- 
basic  radicles  according  to  the  types  in  which  they  occurred. 

Several  years  earlier,  however,  Frankland  reviewed  the  results 
of  his  work  on  organo-metallic  compounds,  and  on  comparing 
these  with  inorganic  compounds  of  the  same  metals,  it  was  seen 
that  each  metal  possessed  a  "  maximum  saturation  capacity," 
i.e.  could  combine  with  a  certain  definite  maximum  number  of 
monobasic  (or  to  use  the  clearer  term,  monatomic)  groups,  and 
no  more.  This  observation  led  in  one  direction  towards  the 
periodic  classification  of  the  elements,  and  in  another  to  the 
establishment  of  the  valence  theory. 

These  views  upon  saturation-capacity,  or  atomicity  or  com- 


THE  HISTORY  OF  ORGANIC  CHEMISTRY     87 

bining  power  were  extended  to  the  case  of  carbon  indepen- 
dently, and  almost  simultaneously,  by  Couper  and  Kekule"  in 
1858. 

Couper  showed  that  carbon  possesses  four  combining  units, 
and  elaborated  a  system  of  graphic  notation  of  the  chief  carbon 
compounds,  which  is  practically  that  in  use  at  the  present  day, 
except  that  he  retained  the  atomic  weight  of  8  for  oxygen,  and, 
consequently,  all  his  oxygen  atoms  are  doubled.  A  couple  of 
examples  will  show  the  similarity  of  his  formulae  to  ours  : — 

cr  o    o  jc  c o OH 

Ether       j  I    2        2 '  I  ;    tartaric  acid     j         » 

/^  TT  TT     /"*  *..••••*! 

(^t±3  w3u  L, o OH 

1 O OH 

C TT 


Kekule's  memoir  on  the  subject  is  on  much  the  same  lines, 
and,  after  establishing  the  quadrivalence  of  carbon,  goes  on  to 
explain  the  nature  of  the  more  complicated  organic  compounds, 
showing  how  these  may  be  built  up  of  chains  of  carbon  atoms 
with  the  other  elements  attached  to  the  atomic  combining  units 
remaining  free  after  two  had  been  used  up  in  the  union  with 
neighbouring  carbon  atoms,  e.g.  :  — 


I    I    I    I    I    I 

Thus,  in  about  five  years  after  Gerhardt  had  united  all  that 
was  best  in  the  radicle  and  type  theories,  his  efforts  had  led  to 
the  further  development  which  soon  ended  in  the  evolution  of 
our  present  structural  ideas. 

It  has  been  said  that  Couper  originated  the  modern  structure 
formula  in  its  present  form  ;  Kekule  devised  a  system  of  graphi- 
cally representing  the  atomicities  of  the  elements  by  the  size  of 
the  symbols,  but,  like  Dalton's  system  of  atom  symbols  half  a 


88  A  SHORT  HISTORY  OF  CHEMISTRY 

century  before,  it  was  found  too  cumbrous  for  daily  use.  Crum 
Brown  introduced  the  method  of  representing  the  graphic 
formula  of  a  compound,  which  is  next  illustrated,  in  1865  :— 

©     ©  ©    © 

II  II 

®-©~©—©-©-©—® 
i        i  il 

©     ©  ©    © 

and,  by  leaving  out  the  circles,  Erlenmeyer  and  Frankland 
reduced  the  notation  a  year  or  two  later  to  the  form  it  now 
holds. 

§  4.  Benzene  and  the  Cyclic  Compounds — The  reader 
will  have  noticed  that  the  compounds  whose  constitutions  were 
gradually  denned  by  the  long  succession  of  hypotheses  cul- 
minating in  the  Frankland-Couper-Kekule  valence  theory  were 
all  of  the  simplest  kind — methane,  alcohol,  citric  acid,  oxalic 
acid,  and  the  like,  or,  in  a  word,  the  "  simpler  fatty  compounds  ". 
Groups  like  benzoyl  and  cinnamyl  and  the  aniline  residue  were 
still  written  empirically,  C7H5O,  C9H7O,  C6H5N,  and  so  on, 
and  no  further  insight  was  gained  into  their  ultimate  composi- 
tion. The  benzoyl  and  cinnamyl  radicles  were  among  the  first 
of  this  class  to  be  discovered,  and  so,  since  these  were  obtained 
from  various  "  essential  oils,"  their  designation  (aromatic)  be- 
came extended  to  the  whole  series  of  bodies  chemically  related 
to  them. 

During  the  ten  years  1858-68,  also,  much  progress  was  made 
in  extending  the  classification  of  fatty  compounds  and  in  dis- 
covering new  compounds  and  preparative  methods  based  on 
applications  of  the  valence  theory,  while  the  study  of  the  aromatic 
compounds  was  always  hampered  by  the  ignorance  of  their 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      89 

fundamental  constitution.  It  was  soon  made  clear  that  any 
theory  which  would  explain  the  facts  must  account  for  the 
comparative  richness  in  carbon  of  the  aromatic  series,  for  the 
circumstance  that  no  known  aromatic  compound  contained  less 
than  six  carbon  atoms,  reduction  of  this  number  leading  to  loss 
of  the  characteristic  properties  displayed  by  the  series,  and  for 
a  general  resemblance  in  chemical  behaviour  running  through 
the  whole  series  and  distinguishing  it  from  the  fatty  com- 
pounds. 

The  credit  of  establishing  such  a  theory  belongs  in  this  instance 
entirely  to  Kekule  (the  valence  theory,  it  will  be  recalled,  was 
divided  between  Couper  and  Kekule).  In  1867  he  stated  that 
all  the  observed  facts  could  be  satisfactorily  explained  by  as- 
suming as  the  characteristic  structure  of  such  compounds  a 
nucleus  of  six  carbon  atoms  united  in  a  ring,  each  atom  having 
its  valencies  so  disposed  as  to  admit  of  union  with  only  one 
monovalent  element  or  group.  Benzene,  the  simplest  member 
(discovered  by  Faraday  in  1825),  was  therefore  formulated  as  :  — 


H—  C(6)     <2)C—  H 
(5)     (3)  C—  H 


— 
H—  C 


The  success  of  his  theory  may  be  best  judged  by  its  results  : 
the  state  of  affairs  in  1867  has  been  so  materially  altered  that 
at  the  present  day  more  aromatic  than  fatty  substances  have 
probably  been  synthesized  in  the  laboratory. 

The  idea  of  a  closed  carbon  chain  was  not  only  applied  to 
the  substances  then  called  aromatic,  however,  but  was  very 
soon  extended  to  classes  containing  elements  other  than  carbon. 
A  commencement  was  made  in  1869,  when  Korner  suggested 


90  A  SHORT  HISTORY  OF  CHEMISTRY 

a  structure  for  pyridine  on  lines  analogous  to  Kekul^'s  benzene 
formula  :  — 

H 

/'C\ 
H—  C  C—  H 

I  II 

H—  C  C—  H 


Many  other  ring-systems,  both  carbocyclic  x  and  heterocyclic, 
have  since  been  brought  into  the  scheme,  and  it  will  probably 
be  simplest  to  draw  up  a  series  of  lists  illustrating  the  chief 
applications  of  Kekule's  theory  to  other  ring-systems. 

1  The  following  terms  are  now  used  to  define  the  various  classes  of 
organic  compounds  :  aliphatic,  derived  ultimately  from  the  paraffin  hydro- 
carbons ;  aromatic,  from  the  benzene  hydrocarbons  ;  carbocyclic  (homo- 
cyclic),  possessing  a  closed  chain  of  carbon  atoms;  heterocyclic,  a  closed 
chain  including  other  elements  as  well  as  carbon  ;  homocatenic,  an  open 
chain  of  carbon  atoms;  heterocatenic,  an  open  chain  of  carbon  and  other 
atoms  ;  alicyclic,  a  fully  saturated  carbon  ring-system  (polymethylenes). 


THE  HISTORY  OF  ORGANIC  CHEMISTRY     91 


(a)  HETEROCYCLIC  RINGS  ANALOGOUS  TO  BENZENE. 

Proof  of  Struc-  Isolation, 

ture. 


1869  Korner  1846  Anderson ;  in  bone- 

oil. 


f  1871  Dewar         1842    Gerhardt ;    from 
1  1878  Grabe  quinine  and  cinchona. 


1883  Riedel  1871   Grabe     and     H. 

Caro  ;       synthesized 
from   diphenylamine. 


1875  Perkin  1875  Perkin's  synthesis. 


(Collie,  1899)          1884  Ost. 


1881  Merz  and       1895    and    ff.      Occur 

Weith  in    nature    as    dyes. 

Kostanecki;   synthe- 


1869  Baeyer  and    1866  Baeyer  ;  reduction 
Emmerling  of  indigo. 


1873  Grabe 


1872  Grabe  ;   in   crude 
anthracene. 


9*       A  SHORT  HISTORY  OF  CHEMISTRY 


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THE  HISTORY  OF  ORGANIC  CHEMISTRY       93 


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94  A  SHORT  HISTORY  OF  CHEMISTRY 

(d)  REDUCED  CARBOCYCLIC  COMPOUNDS. 

The  cyclic  polymethylenes  have  been  prepared  from  the  second  to 
the  eighth  member,  interest  in  this  class  having  been  aroused  by  Baeyer 
about  1881.  The  series  is  interesting  since  it  forms  a  kind  of  intermediate 
stage  between  the  paraffins  (non-cyclic,  saturated)  and  the  aromatic  hydro- 
carbons (cyclic,  unsaturated).  Further,  it  has  contributed  to  our  knowledge 
of  the  steric  conditions  of  the  carbon  atom,  for  in  1885  Baeyer  showed  that 
according  to  van  't  Hoff's  theory  of  the  distribution  of  the  four  carbon  affini- 
ties in  space  (see  §  7)  the  five-  and  six-membered  rings  should  be  formed 
most  easily  and  be  the  most  stable,  since  in  these  positions  the  directions 
of  the  valencies  suffered  least  distortion  when  forming  the  closed  system 
(Baeyer's  Strain  theory). 

The  parent  hydrocarbons  were  obtained  by  the  following  workers : — 

CH2x 

Cyclo-propane,  trimethylene    |         ;CH.>  1882  Freund. 
CHa/ 

OH.,— CH2  1894   W.  H.  Perkin,  jun. 

Cyclo-butane,  tetramethylene    |  (only  the  chloro-  oxy-  and 

CH2— CH2  amido-tetramethylenes). 

CHa  1907   Cyclobutane  : 

/\  Willstatter  &  Bruce. 

Cyclo-pentane,  pentamethylene  CH2     CH2  1893  J.  Wislicenus. 

CHa— CHa 
CH2 

/\ 
CH2    CH2 

Cyclo-hexane,  hexamethylene     I  1894  Baeyer. 

CH2    CH2 


CH, 

/CH2— CH.,— CH2 
Cyclo-heptane,  heptamethylene  CH2Q  |        1893  Markownikow. 

\CH2— CH2— CH2 

(Cyclo-octane)  cyclo-octadiene  1903  Ciamician  and  Silber. 

Cyclo-octane  CH2— CH«— CH2— CH2 

1907  Willstatter  and  Vera- 
CH2— CH2— CH2— CH2  guth. 

/CH2— CH2 — CH2 — CH2 

Cyclo-nonane  CH2<;  1907  Zelinsky. 

\CH2— CH2— CH2— CH2 

Returning  to  the  discussion  of  a  formula  for  benzene,  upon 
'  which  all  the  other  ring-formulae  may  be  said  to  depend,  it  will 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      95 

be  obvious  that  a  considerable  amount  of  laborious  confirmatory 
work  was  necessary  in  order  to  prove  beyond  all  doubt  that 
benzene  really  possessed  the  structure  assigned  to  it  by  Kekule'. 
This  has  been  conscientiously  carried  out  by  a  number  of 
workers  at  different  periods,  and  its  nature  will  best  be  grasped 
by  discussing  it  in  the  order  of  the  problems  which  presented 
themselves  for  solution. 

(a)  The  formula  postulates  a  perfectly  symmetrical  structure 
for  benzene. 

This,  or  in  other  words,  the  equivalence  of  the  hydrogen  atoms  in 
benzene  has  been  proved  by  Ladenburg  (1874),  Wroblewski  (1872-8), 
and  others  by  replacing  all  the  different  hydrogen  atoms  in  turn  by  the 
same  group,  the  same  product  being  invariably  obtained. 

(b)  It  demands  the  presence  of  a  closed  chain  of  carbon 
atoms. 

The  proof  of  the  ring-structure  was  really  completed  by  W.  H.  Perkin, 
jun.  (1891-4)  when  he  synthesized  various  derivatives  of  hexahydrobenzene 
as  well  as  the  hydrocarbon  itself,  and  obtained  products  identical  with 
those  obtained  by  reduction  of  the  benzene  molecule  (Baeyer,  1887-92). 

(c)  It  suggests  the  existence  of  one  mono-substitution-pro- 
duct, three J  di-  and  three  tri-substitution  products  of  benzene 
by  one  kind  of  group. 

This  problem,  "orientation,"  was  one  of  the  most  troublesome  to  solve, 
and  some  years  elapsed  before  definite  proof  was  forthcoming  that  the  theory 
was  here  in  full  accordance  with  the  facts.  The  main  factors  contributing 
to  the  final  satisfactory  proof  were  as  follows : — 

1871.  Baeyer  showed  that  phthalic  acid  (from  naphthalene  by  oxidation) 
is  ortho-(i,  2)-dicarboxyl-benzene,  and  that  isophthalic  acid  (from  iso- 
xylene,  produced  in  turn  from  mesitylene)  is  meta-  (i,  3)-dicarboxyl-benzene, 
so  that  terephalic  acid  must  be  the/ara-(i,  4)-compound. 

1874.  Korner  showed  that  an  or^Ao-di-substitution  product  should 
yield  two,  a  meta-  three,  and  a^ara-  only  one  tri-substitution  product,  and 
on  this  basis  determined  the  orientation  of  the  three  known  dibromobenzenes. 

1  Excluding  the  possible  second  diortho-substituted  substances,  referred 
to  later. 


96  A  SHORT  HISTORY  OF  CHEMISTRY 

1872.  Griess  proved  that  of  the  six  known  diamino-benzoic  acids,  two 
gave  one  diamino  body,  three  gave  another,  and  one  another.  Arguing 
conversely  to  Korner,  he  arrived  at  the  same  conclusion  respecting  the 
orientation  of  the  di-substitution  products. 

1875.  Ladenburg,  by  a  complicated  process,  gave  definite  evidence  that 
nresitylene  was  i,  3,  5  trimethylbenzene,  thereby  confirming  Baeyer's  de- 
ductions regarding  isophthalic  acid. 

These  combined  proofs  put  the  practical  utility  of  Kekule's 
theory  beyond  all  doubt,  but  there  has  always  been  one  uncer- 
tain point  with  reference  to  it,  namely,  the  disposal  of  the  fourth 
valency  of  each  combination.  Kekule  represented  these  as 
forming  three  pairs  of  ethylenic  bonds,  but  the  stability  and 
general  chemical  behaviour  of  aromatic  derivatives  are  entirely 
opposed  to  such  an  accumulation  of  ordinary  fatty  "  unsaturated 
Unkings".  Between  1887  and  1892  Baeyer  carried  out  an 
enormous  series  of  experiments  on  the  reduction  of  various  car- 
boxylic  acids  of  benzene,  with  a  view  to  clearing  up  this  point, 
but,  although  numerous  important  observations  were  made  in 
various  directions,  the  main  object  of  the  inquiry  was  not  attained. 

Another  line  of  attack  was  the  physical  properties  of  benzene. 
We  shall  see  in  Chap.  x.  (p.  181)  how  the  numerical  values  of 
various  physical  properties  are  sometimes  adapted  for  showing 
the  constitution  of  a  substance.  It  is  possible  in  this  way  to 
calculate  different  values  for  benzene  according  to  different 
formulae  which  it  may  possess,  and  to  compare  these  values 
with  that  found  for  a  given  property  by  experiment.  This  has 
been  done  by  Schiff  (1883)  and  Horstmann  (1887)  with  mole- 
cular volume,  by  Briihl  (1894)  with  refractive  index,  and  by 
Thomsen  (1880),  and  Stohmann  (1893)  with  reference  to  heats 
of  combustion  of  benzene  and  various  derivatives,  but  the 
results  are  conflicting  and  do  not  all  point  to  the  same  for- 
mula. 

A  property  which  seems  to  shed  a  little  more  light  on  the 
problem  is  the  absorption  spectrum  of  benzene,  studied  by 
Baly  and  Collie,  and  by  Hartley,  and  referred  to  again  later  in 
this  paragraph. 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      97 


Numerous  formulae  have  from  time  to  time  been  proposed 
in  order  to  account  for  the  remaining  valencies  of  the  car- 
bon atoms.  These  can  be  divided  into  two  classes,  static  and 
dynamic,  according  as  the  component  atoms  are  conceived  in  a 
state  of  rest  or  motion. 

The  "diagonal"  formula   was   the  first  of  the 
former  type,  and  was  suggested  by  Claus  in  1867. 

It  bears  an  apparent  resemblance  to  the  Arm- 
strong-Baeyer  "centric"  formula  (1892),  which  supposes  the 
extra  valencies  to  be  directed  to  the  centre  of  the 
benzene   nucleus,   so  as   mutually  to  satisfy  each 
other.       (In    1869    Ladenburg    put    forward    his 
"prism"   formula,   which  was  later  refuted,  chiefly  owing  to 
Baeyer's  work  on  the  reduced 
benzoic  acids.) 

The  Armstrong-Baeyer  con- 
ception of  the  benzene  molecule 
was  extended  by  Bamberger 
to  numerous  six-membered  rings,  both  carbo-  and  hetero -cyclic. 
He  succeeded  in  explaining  by  its  means  certain  characteristic 
reactions  of  "  conjugated  aromatic  nuclei,"  such  as  those  in  the 


napthalene 


anthracene 


and 


series, 


especially  showing  why  reduction  products  such  as,  e.g. 
7 


q"i"°ii™  O 


98  A  SHORT  HISTORY  OF  CHEMISTRY 

CH2 
XX 

CH 

(ar)-tetrahydro-a-naphthol 

CH 

^ 


should  behave  as  aromatic  substances  while  those  like 

CH, 

(ac)-tetrahydro-a-naphthol  (/       sj  Jen 


resemble  the  fatty  series  more  nearly  in  chemical  behaviour. 

No  one  believes  at  the  present  time  that  the  atoms  in  any 
compound  are  at  rest,  i.e.  always  remain  in  the  same  relative 
positions,  and,  therefore,  it  is  more  interesting  to  review  the 
attempts  made  to  account  for  the  constitution  of  benzene  on 
dynamical  grounds.  Kekule  himself  saw  that,  in  addition  to 
the  questionable  existence  of  "  double  bonds  "  in  benzene,  his 
original  formula  involved  the  possibility  of  two  ortho-di-substi- 
tution  products  if  the  substituting  groups  were  not  the  same. 
He,  therefore,  suggested  (in  1872)  that  the  fourth  valency 
oscillated  between  the  carbon  atoms,  thus  :  — 

s\          / 

i   ii    ^    i 


Knorr,  in  1894,  owing  to  his  experiments  on  methyl  pyrazole 
(cf.  §  5),  assumed  that  the  hydrogen  atoms,  rather  than  the 
carbon  linkings,  were  in  a  state  of  oscillation.1 

1  It  may  be  remarked  that  in  a  few  instances  such  isomeric  diortho 
compounds  have  been  obtained,  e.g.  two  o-nitrotoluenes.  The  difference»s 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      99 

On  the  other  hand,  Thiele  arrived  at  quite  a  different  formula 
in  1899,  based  on  his  theory  of  "partial  valencies"  (chap,  iv., 
p.  54).  Starting  from  Kekule's  formula,  he  obtained  the  new 
formula  for  benzene  as  follows  : — 


;M 

Her     UGH 


CH 


The  most  comprehensive  formula  of  benzene  is  that  proposed 
by  Collie  in  1897.  He  assumes  that  each  carbon  atom  is 
vibrating,  and  that  consequently  the  relative  positions  of  the 
atoms  are  always  altering.  In  this  way  the  molecule  passes 
and  repasses  through  a  series  of  phases,  isolated  phases  being 
represented,  as  a  matter  of  fact,  by  formulae  such  as  Kekule's 
and  the  centric  arrangement.  An  interesting  point  is  that  in 
this  system  there  are  seven  possible  ways  of  making  and  break- 
ing the  "  linkings  "  of  the  carbon  atoms  during  a  complete 
vibration,  and  these  may  possibly  give  rise  to  the  seven  "  ab- 
sorption bands  "  in  the  ultra-violet  spectrum  of  benzene.  It 
should  be  observed  that  Collie's  formula  is  steric,  i.e.  it  pictures 
other  atoms  as  they  are  arranged  in  space,  not  simply  as  a  plane 
projection  of  the  spacial  configuration. 

Other  steric  but  static  benzene  formulae  (all  based  upon 
van  't  Hoff's  conception  of  the  carbon  atom  as  acting  at  the 
centre  of  a  regular  tetrahedron,  with  its  valencies  directed  to- 
wards the  apices)  had  been  previously  put  forward,  notably  by 

between  the  two  forms  are  very  slight,  and  lie  entirely  in  physical  proper- 
ties (Knoevenagel).     The  phenomenon  has  been  termed  "  moto-isomer- 

ism  ". 


ioo         A  SHORT  HISTORY  OF  CHEMISTRY 

Baeyer  (1888)  and  Vaubel  (1891),  whose  attempts,  however,  do 
not  satisfactorily  account  for  the  phenomena  shown  on  reduc- 
tion of  the  benzene  nucleus  by  hydrogen.  Sachse  (1890) 
represented  the  most  stable  and  symmetrical  grouping  of  the 
atoms  by  six  tetrahedra  superposed  upon  six  faces  of  a  regular 
octahedron,  leaving  two  parallel  faces  vacant.  Both  Thiele 
and  Briihl  supported  Sachse's  view. 

The  whole  position  may  be  summed  up  by  saying  that  at 
present  Collie's  formula  offers  the  most  satisfactory  theoretical 
explanation  of  the  variety  of  experimental  data,  while  for 
ordinary  practical  purposes  Kekule's  original  "  hexagon  "  still 
suffices. 

§  5.  Dynamic  Isomerism—  The  most  interesting  develop- 
ments of  organic  theory  during  recent  years  have  centred  round 
isomerism  of  one  kind  or  another,  and  in  the  following  para- 
graphs we  shall  deal  with*  the  progress  of  our  knowledge  of  the 
chief  kinds  of  isomerides. 

Numerous  substances  are  now  known  which  react  under 
different  conditions  as  though  they  possessed  different  struc- 
tural formulae,  in  other  words,  as  though  the  same  sub- 
stance combined  in  itself  the  properties  of  two  isomeric 
compounds.  A  notable  early  example  was  that  of  isatin 

CO  CO 

.  OH  (labile)  or  C6H  /\CO    (stable)      (Baeyer, 


N  NH 

1883)  ;  two  years  later  Laar  called  attention  to  other  instances 
(nitrosophenol,  acetoacetic  ester,  etc.)  and  suggested  for  the 
phenomenon  the  name  tautomerism. 

Isomerism  of  this  type  has  probably  been  more  discussed 
in  the  case  of  acetoacetic  ester  than  of  any  other  single 
substance.  This  body  was  discovered  in  1863  by  Geuther, 
who  formulated  it  as  CH3  .  C(OH)  :  CH  .  COOC2H5,  while 
Frankland  believed  it  to  be  ketonic,  CH8  .  CO  .  CH2  .  COOC2H6. 


THE  HISTORY  OF  ORGANIC  CHEMISTRY  '-  te 


Both  the  mechanism  of  its  formation  and  its  chemical  properties 
have  furnished  difficulties  ;  the  latter  tend  to  show  that  it  reacts 
sometimes  in  the  hydroxylic  and  sometimes  in  the  ketonic 
form.  As  these  two  forms  are  characteristic  of  the  tauto- 
merism  displayed  by  many  compounds,  a  convenient  nomen- 
clature was  suggested  for  them  by  Briihl  in  1893,  viz.  the  enol- 
(hydroxylic)  and  kefo-  (ketonic)  forms. 

A  historical  survey  of  tautomerism  must  include  an  account 
of  the  chief  tautomers  discovered,  of  the  methods  applied  in 
their  investigation,  and  of  the  theories  put  forward  to  explain  the 
mechanism  of  the  changes  involved. 

The  chief  examples  of  tautomeric  substances  so  far  known 
are  included  in  the  following  summary  ;  those  discovered  before 
the  advent  of  modern  structural  views  were,  needless  to  say, 
only  realized  to  be  desmotropic  (to  use  an  equivalent  term 
coined  by  Jacobson  in  1887)  at  a  much  later  date. 

The  summary  may  conveniently  be  divided  into  the  two  main 
kinds  of  tautomers  :  — 

(a)  Substances  reacting  in  two  forms,  but  only  isolable  in 
one. 

(b)  Substances  reacting  in  two  forms,  both  of  which  can  be 
isolated. 


102         A  SHORT  HISTORY  OF  CHEMISTRY 


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THE  HISTORY  OF  ORGANIC  CHEMISTRY      103 

(b)  Different  Forms  Isolated.  Chief  Worker. 

Tribenzoylmethane  One  enol  and  one  keto  1893  Claisen. 

Mesityloxideoxalic  ester  „  1896  Claisen. 

Phenylnitromethane  Hydroxylic  (acid)  and  non-     1896  Hantzsch. 

hydroxylic  (^-acid) 

Formylphenylacetic  ester        One  enol  and  one  keto  1896  W.  Wislicenus. 

Dibenzoylsuccinic  ester  Various  di-keto,   keto-enol     1896  Knorr. 

and  di-enol  forms 
Diacetylsuccinic  ester  Various  di-keto,   keto-enol     1896  Knorr. 

and  di-enol  forms 
Benzylidene  diacetylacetone    Various  di-keto,  keto-enol    1899  SchifT, 

and  di-enol  forms 

Camphor-quinone     phenyl-     Normal     hydrazone     and     1899  Betti. 
hydrazone  oxy-azo  forms 

Arguments  based  upon  both  chemical  and  physical  properties 
have  naturally  been  used  in  attacking  the  problem,  but  the 
bulk  of  those  derived  from  chemical  changes  have  been  proved 
within  the  last  ten  or  twenty  years  to  be  invalid,  since  the 
different  reagents  used  were  shown  to  have  first  produced  a 
particular  isomer,  which  then  entered  into  the  reaction.  Thus 
some  reagents  furnish  the  keto-,  others  the  enol-isomer ;  some 
exert  a  ketonizing,  others  an  enolizing,  effect.  For  this  reason, 
all  acidic  or  alkaline  reagents  have  been  banned,  and  chemists 
have  found  very  few  suitable  reagents  for  tautomeric  investigation 
by  chemical  means;  Schiff  (1898)  used  benzalaniline,  which 
unites  with  either  enol-  or  keto-acetoacetic  ester,  yielding 
entirely  different  products.  Phenyl  isocyanate  has  been  used  to 
detect  hydroxyl  or  amino  groups  in  desmotropic  compounds,  and 
sometimes  alcoholic  ferric  chloride  will  show  the  presence  of  an 
enol-form  without  disturbing  the  constitution  of  the  isomer 
(W.  Wislicenus,  1896). 

Study  of  the  physical  properties  has  naturally  often  proved 
much  more  successful;  differences  in  the  values  of  different 
forms  of  keto-enol  isomers  were  found  by  W.  H.  Perkin,  sen. 
(1892)  for  magnetic  rotation,  Traube  (1896)  for  molecular 
volume,  and  Briihl  (1899)  for  refractive  and  dispersive  power. 
Hantzsch  traced  the  change  of  acids  (R.CH:NO.OH) 


OH 


io4         A  SHORT  HISTORY  OF  CHEMISTRY 

to    pseudo-acids    (R  .  CH2  .  NO2),    and    of    ammonium    bases 
C«H5  C6H6 

c  x 

C  H         ^C  H         to    \\f-ammonium    bases        C6H4v        / 

xN\  I 

CH3       OH  CH3 

by  electrical  conductivity  measurements  in  1896,  and  in  the 
same  year  Wislicenus  followed  the  keto-  ^  enol  change  by  a 
colorimetric  method  based  upon  the  intensity  of  colour  furnished 
by  a  standard  alcoholic  ferric  chloride  solution.  Similarly, 
solubility  and  melting-point  curves  have  been  studied  by 
Lowry  (1904),  Knorr  and  others,  while  Hartley  and  others  have 
examined  the  absorption  spectra  of  tautomeric  compounds. 
Another  property  which  is  especially  delicate  when  it  can  be 
applied  is  alteration  in  optical  activity  or  mutarotation,  as  Lowry 
has  termed  it  ;  he  has  applied  the  method  to  the  isomerism  of 
nitro-  and  bromo-camphor  and  of  a-  and  y-glucose. 

The  theories  of  tautomeric  change  are  chiefly  associated  with 
the  names  of  Butlerow  (1877),  Laar  (1885),  Knorr  (1894-95), 
Lapworth  (1902),  and  Lowry  (1904).  Laar  held  the  pheno- 
menon to  be  due  to  the  rapid  oscillation  of  particular  linkings  in 
the  molecule,  his  explanation  being  thus  intramolecular.  Knorr, 
on  the  other  hand,  considered  the  process  to  be  intermolecular, 
molecules  of  either  isomer  being  present,  but  continually  chang- 
ing into  the  alternate  form  ;  for  instance,  with  methylpyrazole 
(1894)  obtained  from  two  isomeric  phenyl  methylpyrazoles  :— 


/\ 
CH3.C  N  -*.        CH3.C          NH 

CH  —   CH  CH  =  CH 

In  other  words,  the  hydrogen  atom  oscillates,  rather  than  the 
double  linkings.  In  1899  he  stated  further  that  tautomers  tend 
in  general  to  form  an  equilibrium  ("  allelotropic  ")  mixture  of 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      105 

constant  composition,  the  examples  where  only  one  form  is 
known  being  limiting  cases  of  this  rule.  He  had  also,  four  years 
earlier,  expressed  the  conviction  that  the  isomerizing  effects  pro- 
duced by  different  reagents  were  really  due  to  the  action  of  ions, 
and  in  1902  Lapworth  removed  various  discrepancies  which 
occur  if  ordinary  acid  or  alkaline  ions  are  assumed  to  produce 
the  effect  by  suggesting  the  changes  were  essentially  caused 
only  by  the  action  of  organic  ions. 

Lowry  in  1904  introduced  the  term  dynamic  isomerism  to 
embrace  all  the  forms  of  isomerism  previously  classed  as  tauto- 
merism,  desmotropism,  etc.  He  showed  that  tautomeric  changes 
could  be  treated  mathematically  by  the  law  of  mass  action,  just 
like  ordinary  chemical  "reactions  of  the  first  order,"  the 
velocity  constants  for  typical  cases  having  been  previously 
worked  out  by  himself  in  1899  (optical  activity  of  camphor 
derivatives)  and  by  Kiister  (1895).  He  assumed,  too,  that  the 
mechanism  of  the  change  was  a  catalytic  action  due  to  the 
presence  of  ions. 

Finally,  in  1904-5,  Baly  and  Desch  put  forward  an  explana- 
tion, different  from  any  of  the  above.  Since  simple  hydroxylic 
or  ketonic  substances  show  no  "absorption  band"  in  the 
ultra-violet  spectrum,  while  keto-enolic  dynamic  isomers 
usually  possess  one,  they  considered  that  the  alteration 

\C  =  O->  =  C  —  OH  is  responsible  for  the  production  of  the 

band,  i.e.  tautomerism  phenomena  are  due  to  vibrations  in  the 
molecule  caused  by  the  constant  structural  alteration. 

§  6.  Sterio  Hindrance — A  problem  not  unconnected  with 
those  reviewed  in  the  two  preceding  sections  is  that  known 
latterly  as  "  steric  hindrance  ".  From  time  to  time  exceptions 
have  been  found  to  reactions  which  generally  take  a  well-defined 
course,  and  in  many  cases  it  has  seemed  probable  that  the  cause 
of  the  anomaly  is  the  near  presence  of  other  non-reacting 
groups  in  the  molecule  which,  apparently,  protect  the  reacting 
radicle  from  attack  by  reason  of  their  bulk.  Victor  Meyer  was 


106         A  SHORT  HISTORY  OF  CHEMISTRY 

the  main  author  of  this  theory  of  steric  hindrance,  which  dates 
from  about  1894.  The  chief  examples  noticed  previous  to  his 
work  are : — 

1872  Hofmann  Substituted  anilines  such  as  C6(CH3)5NH2,  do  not 
yield  quaternary  ammonium  iodides  of  the  type 
R .  NR3I. 

1883-84  ,,  The    nitrile  group    of  certain   highly  substituted 

benzonitriles  could  not  be  saponified  in  the  usual 
way. 

1891-92     Claus          Noticed  that  the  di-ortho-substituted  cyanides  were 
especially  hard  to  saponify,  but  that  the  nature 
of  the  substituent  also  modified  the  reaction. 
1890    Pinner        Ortho-substituted  cyanides  do  not  readily  give  imino- 

ethers  R .  C\ 

\OEt 

1890  Kehrmann  Ortho-substituted  quinones  do  not  readily  give  oximes. 

1891  V.  Meyer  „  „  „  „          hydra- 

zones. 

V.  Meyer  was  thus  led  to  examine  the  rates  of  esterification  of 
a  long  series  of  substituted  benzoic  acids,  and  found  that  while 
the  reaction  proceeded  equally  well  on  the  whole  when  the 
silver  salt  of  the  acid  was  heated  with  ethyl  iodide,  yet  by 
the  usual  hydrochloric  acid  method  very  varying  results  were 
obtained.  These  led  to  his  "  Esterification  Law  ".  In  the 
substituted  benzoic  acids,  the  presence  in  the  ortho-position 

COOH 

-^  to  the  carboxyl  group  of  a  radicle  of  low  molecu- 
lar weight  retards  esterification,  while  groups   of 


higher  molecular  weight  may  altogether  prevent  it. 

In  1899  the  extension  of  Meyer's  researches  to  the  substituted 
fatty  acids  was  undertaken  by  Sudborough,  showing  that  sub- 
stituents  in  the  methylene  group  next  to  the  carboxyl  behave 
in  the  same  manner  as  ortho-substituents  in  benzoic  acid,  whiv° 
in  1895  and  1897  Meyer  and  Kellas  respectively  showed  th 
those  esters  which  are  formed  with  difficulty  are  also  the  hardes 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      107 

to  hydrolyze,  showing  clearly  the  "protecting  "  influence  of  the 
adjacent  radicle. 

Other  instances  of  steric  hindrance  occur  in  Bischoff  s  inves- 
tigations as  to  the  conditions  which  influence  chain- formation 
in  the  malonic  and  aceto-acetic  ester  syntheses  (i 880-8)  ; 
Schryver  (1899)  showed  that  the  sodium  salts  of  ortho-  and 
para-nitrophenols,  and  di-ortho-bromophenols  do  not  give 
the  general  reaction  with  camphoric  anhydride,  forming  aryl 
hydrogen  camphorates. 

The  fact  that  other  influences  besides  the  size  of  the  molecule 
niiy  sometimes  partially  or  completely  mask  the  hindering  effect 
is  shown  by  the  rates  of  reaction  of  sodium  hydrogen  sulphite 
with  various  substituted  ketones  (Stewart,  1905),  and  by  the 
sulphination  of  a  series  of  phenolic  ethers  : — 

R .  C6H4 .  OEt  ->  R  .  C6H3(OEt)(S02H)  ->  [R  .  C6H3(OEt)]2SO 
->  [R  .  C6H3(OEt)]3S.  OH . 

The  stage  to  which  the  latter  reaction  proceeds  is  found  to 
depend  upon  : — 

(a)  The  steric  hindrance  due  to  the  presence  of  ortho-substi- 
tuents. 

(b)  The   directing   influence   of    the   alkoxyl   (OEt)   group 
(Smiles  and  Le  Rossignol,  1908). 

§  7.  Stereo-isomerism  (a)   Geometrical  Isomerism— 

There  are  two  other  kinds  of  isomerism  remaining,  which  have 

been  explained  by  considerations  of  the  arrangement  of  the 

groups  in  space  about  the  central  carbon  atoms  of  the  organic 

molecule.     The  first  which  will  be  discussed  is  that  which 

manifests  itself  most   markedly   in   chemical   properties ;  the 

second,  which  has  been  known  for  a  much  longer  period  than 

the  first,  is  an  isomerism  embracing  three  (or  four)  isomers  in 

each  instance,  which  in  general  differ  mainly  in  their  effect  upon 

upolarized  light.     In  either  case  we  must  first  recapitulate  the 

t;,  views  adopted  as  to  the  nature  of  the  carbon  atom  before  the 

j  development  of  the  theories  of  geometrical  and  optical  isomers 

can  be  understood. 


loS         A  SHORT  HISTORY  OF  CHEMISTRY 

Kekule"s  views  of  organic  structure  were  based  upon  the 
quadrivalency  of  carbon  ;  the  disposition  of  the  valencies  in 
space  was  not  considered.  As  we  have  seen,  his  theories,  espe- 
cially that  dealing  with  benzenoid  compounds,  cleared  up  the 
constitution  of  multitudes  of  compounds,  but  still  there  re- 
mained cases  of  isomers  which  were  unaccounted  for,  such  as 
that  existing  between  maleic  and  fumaric  acids  or  between  the 
four  tartaric  acids. 

Van  't  Hoff  set  out  in  1874  to  try  to  solve  the  problem  by 
obtaining  an  idea  of  the  arrangement  of  the  groups  about  a 
carbon  atom.  Starting  from  the  known  fact  of  the  equivalence 
of  the  hydrogen  atoms  in  methane  he  argued  that  the  disposi- 
tion of  groups  must  be  either  : — 

a  c 


(a)  A  plane  arrangement,  such  as 

X  \ 

b  d 

(l>)  A  space  arrangement  whereby  the  affinities  would  be 
inclined  equally  to  one  another  and  directed  towards  the  carbon 
atom  (the  familiar  tetrahedron). 

Since  (a)   involves    isomerism  H\C//C  \C/^ 

of  substances,   e.g.  j^X  '\Q         Q/  '\H 

such  as  is  contrary  to  observed  fact,  the  alternative  (/;)  must  be 
taken. 

Le  Bel  introduced  practically  the  same  view  of  the  carbon 
atom  at  the  same  time,  but  independently  of  van  't  Hoff. 

According  to  this  view  the  atoms  of  substances  containing  an 
ethylenic  bond  would  be  so  arranged  in  space  that  the  four  re- 
maining groups  would  all  lie  in  one  plane,  and  as  the  double 
linking  would  prevent  free  rotation  of  the  central  carbon  atoms, 
geometrical  isomerism  might  be  expected  :— 

a  cad 

\C  =  C<^      and      ^)C  =  C<^    ; 
b  d  b  c 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      109 

a  a  a  b 

\C  =  cS      and     ^>C  =  C<^  ,  etc. 
b  b  b  a 

During  the  next  ten  years  J.  Wislicenus  examined  many  cases 
of  such  geometrical  isomerism  in  ethylenic  compounds  and 
published  his  results,  "  Die  raumliche  Anordnung  der  Atome," 
in  1887.  The  isomers  used  were  maleic  and  fumaric,  crotonic 
and  iso-crotonic,  citraconic  and  mesaconic,  oleic  and  elaidic 
acids,  etc.,  stilbenes  (CGH5 .  CH  :  CH  .  C6H5),  tolanedihalides 
(C6H5  .  CX  :  CX  .  CCH5),  and  many  others. 

In  1892  Baeyer  introduced  convenient  terms  for  the  two 
kinds  of  isomers,  viz.  : — 


b  c  b  a 

Cis-compound.  Trans-compound. 

In  the  preceding  years  he  had  prepared  a  series  of  similar 
isomers  in  the  case  of  some  of  his  reduced  aromatic  acids. 

The  "  configuration  "  (cis-  or  trans-)  of  the  isomers  was 
based  by  J.  Wislicenus  chiefly  on  the  ability  to  yield  anhydrides 
or  cyclic  compounds,  and  the  formation  from  the  correspond- 
ing acetylene  derivative  in  the  case  of  cis-compounds,  while 
superior  stability  and  characteristic  physical  properties  served 
to  point  out  the  trans-compounds. 

Some  other  cases  of  geometrical  isomerism  must  be  briefly 
referred  to  : — 

(a)  Stereo-isomeric  Oximes,  %>  Cl  N .  OH.  —  In    1883 

^2 

V.  Meyer  and  Goldschmidt  obtained  two  benzildioximes, 
C6H5 .  C( :  NOH)  .  C(  :  N  .  OH) .  C6H5,  and  five  years  later 
V.  Meyer  and  Auwers  also  prepared  two  benzilmonoximes,  a 
third  dioxime  being  added  in  1889.  Their  explanation  of 


i io         A  SHORT  HISTORY  OF  CHEMISTRY 

the  isomerism  was  soon  seen  to  be  faulty ;  meanwhile  Beck- 
mann  had  obtained  two  benzaldoximes,  which  he  formulated  as 

O 

(a)  C6H5    CH  =  N  .  OH  and  (ft)  /  \ ,  a  view  which 

C6H5 .  CH  .  NH 

was  speedily  disproved  by  Goldschmidt. 

In  1890  Hantzschand  Werner  put  forward  their  theory,  which 
is  simply  an  extension  of  van  't  Hoff's  views  to  the  — CH  :  N— 
system,  based  on  the  assumption  that  the  three  nitrogen  valencies 
are  directed  to  the  apex  of  a  regular  tetrahedron,  so  that,  for 
instance,  R  .  CH  :  N .  OH  may  be  spacially  represented  as  :— 

This  represents  the  isomerism  as  similar 
to  the  .  CH  :  CH  .  cases,  and  the  chemi- 
cal and  physical  characteristics  of  the 
isomeric  oximes  quite  agree  with  this  view, 
while,  further,  the  isomerism  appears  and 
vanishes  in  accordance  with  the  theory. 
In  cases  where  only  one  oxime  is  known 
it  is  assumed  that  one  of  the  radicles 
has  a  pre-eminently  strong  attraction  for  the  hydroxyl  group. 

The  configuration  of  these  isomers  (termed  syn-  and  anti-  by 
Hantzsch,  previously  to  Baeyer's  cis-  and  trans-}  has  been 
determined  by  : — 

(i)  Ready  conversion  of  one  (the  syn-)  form  to  a  nitrile  by 
loss  of  H2O. 

(ii)  The  "  Beckmann  change,"  which  takes  place  as  follows  in 
presence  of  PC16  or  HC1  and  H2SO4  :— 

a.C.6  /a.C.OHx  a .  CO 

I!  (II        I        -*  I 

N.OH  \    N.b     /  NH.i; 

a.  C.b  /HO.  C.b\          CO  .  b 


/HO.C.JK 
I    I 

V     a.N      / 


HO.N  \    a.N      /         NH.a. 

(iii)  Patterson  and  McMillan  (1908)  have  followed  the  con- 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      in 

version  of  labile  into  stable  isomeric  oximes  dissolved  in  ethyl- 
tartrate  by  means  of  the  varying  rotating  power  of  the  solvent. 

QH6\ 

(b)  Stereo-isomeric  Benzhydroximic  Ethers  /C  :  N  .  OIL 


—  These,  observed  by  Lossen  in  1872,  have  been  explained  by 
Werner  (1892-6)  on  the  Hantzsch-  Werner  hypothesis. 

(c]  Stereo-isomeric  Hydrazones  (Hantzsch,  1890)  and  osazones 
(Anschiitz,  1895)  have  also  been  noticed. 

(d)  Isomeric  Diazo-compounds.  —  In  1863   Griess  discovered 
the  diazo-compounds  and  isolated  potassium  benzene  diazo- 
tate,  C6H5N2OK.    In  1894  Schraube  and  Schmidt  obtained  a 
second  potassium  salt  by  using  different  experimental  condi- 
tions.   Hantzsch  forthwith  assumed  the  differences  to  be  due  to 
geometrical  isomerism,  viz.  :  — 


C6HB.N  C6H6.N 

II  and  || 

KO  .  N  N  .  OK. 


The  previous  formulae  for  diazo-bodies  were  Kekule's  azo- 
formula,  C6H5 .  N  :  N  .  X  (1867),  and  Blomstrand's  diazonium 

C  FT 

formula,     6X5>N  •  N  (1875),  an<^  to  these  two    Bamberger 

referred  the  isomeric  diazotates.  There  ensued  a  protracted 
controversy  between  Hantzsch  and  Bamberger,  in  the  course 
of  which  other  isomeric  diazo  bodies  (diazosulphates  and 
cyanides)  were  obtained. 

Finally,  it  was  generally  admitted  that  both  views  were  prob- 
ably correct ;  while  the  Blomstrand  formula  probably  better 
expresses  the  constitution  of  the  salts  of  strong  acids,  the 
isomerism  of  derivatives  of  weaker  acids  is  to  be  explained  upon 
a  stereo- chemical  basis. 

§  8.  Stereo-isomerism  :  (£)  Optical  Isomerism — In  1815 
Biot  noticed  that  sugar  solutions  rotate  the  plane  of  polarized 
light,  a  phenomenon  previously  observed  in  quartz  by  Arago 
(1811).  In  1819  he  showed  that  a  substance  which  is  thus 


ii2         A  SHORT  HISTORY  OF  CHEMISTRY 

"optically  active"  in  the  liquid  remains  so  in  the  gaseous  state. 
In  1820  Herschel  pointed  out  that  it  was  enantiomorphous 
(quartz)  crystals  which  deviated  polarized  light,  and  Pasteur, 
thirty  years  later,  found  that  sodium  ammonium  tartrate  crystals 
were  also  enantiomorphous  (i.e.  possessed  forms  which  were 
mirror  images  of  each  other),  the  two  kinds  of  crystals  moreover 
yielding  respectively  dextro-  and  laevo-tartaric  acids.  Pasteur 
suggested  that  the  mutual  cause  of  the  hemihedral  crystals  and 
of  the  optical  activity  lay  in  some  asymmetry  of  the  atomic 
structure.  Finally,  in  1873,  J.  Wislicenus  showed  that  the 
isomerism  of  the  lactic  acids  from  flesh  and  from  sour  milk 
(cf.  p.  77)  also  manifested  itself  by  the  optical  activity  of  one 
form,  and  stated  that  the  cause  must  be  connected  with  the 
spacial  disposal  of  the  atoms. 

Then,  in  1874,  came  the  Le  Bel-van  't  Hoff  theory  of  the 
spacial  arrangement  of  atoms,  which  accounted  for  the  exist- 
ence of  more  than  one  derivative  of  substances  containing  an 
"  asymmetric  carbon  atom  ". 


It  may  be  said  that  all  optically  active  compounds  have  been 
found  to  possess  asymmetry  of  this  nature,  although  the 
converse  is  not  yet  experimentally  true  in  some  cases.  Such 
compounds  have  been  known  for  so  long  and  are  so  numerous 
that  examples  are  superfluous.  The  number  of  isomers  of  a 
compound  containing  one  asymmetric  atom  is  in  general  three 
— a  dextro-,  laevo-  and  racemic  isomer  ;  the  two  former  are  alike 
in  all  properties  but  rotating  power,  in  which  they  are  opposite  ; 
the  latter  usually  varies  somewhat  in  physical  properties  from 
the  optically  active  compounds.  A  fourth  stereo-isomer  of 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      113 

tartaric  acid,  meso-tartaric  acid,  was  discovered  by  Pasteur  and 
explained  by  van  't  Hoff  as  a  compound  in  which  the  rotation 
of  one-half  of  the  molecule  was  compensated  by  that  of  the 
other  half.  The  justice  of  this  view  was  proved  in  1892  when 
E.  Fischer  reduced  mucicacidCOOH[CH2OH]4COOH  (another 
meso  compound)  to  galactonic  acid  CH2OH[CH  .  OH]4COOH, 
which  being  no  longer  an  internally-compensated,  but  rather  an 
externally-compensated  (racernic)  molecule,  was  successfully 
split  up  into  active  isomers.  The  meso  isomers  possess  well- 
marked  physical  differences  from  the  other  forms. 

The  correctness  of  Kekule's  benzene  theory  has  often  been 
tested  by  attempting  to  obtain  optically  active  forms  of  the 
benzene  molecule.  Such  experiments  (Le  Bel,  1882  ;  Lewko- 
witsch,  1888  ;  V.  Meyer  and  Liihn,  1895)  have  always,  by  their 
failure,  afforded  good  negative  proof  of  Kekule's  views. 

A  curious  anomaly  found  in  optical  activity  is  that  known  as 
the  Walden  inversion  ;  an  active  compound  usually  yields  by 
chemical  change  a  new  active  compound  of  the  same  general 
sign,  but  Walden  (1895)  found  that^-malic  acid  yielded  /-chloro- 
succinic  acid  with  PC15,  while  the  latter  gave  /-malic  acid  or 
</-malic  acid  according  as  silver  or  potassium  hydroxides  were 
used  to  remove  the  halogen.  Other  similar  instances  have 
been  discovered  (Purdie,  1895). 

Quantitative  Theories  of  Optical  Activity, — In  1890  the  idea 
of  a  molecular  asymmetry-product^  the  value  of  which  was  con- 
ceived possibly  to  be  parallel  with  the  degree  of  optical  activity, 
was  evolved  independently  by  Crum  Brown  and  by  Guye. 
Crum  Brown  assumed  that  each  attached  group  exercised  an 
influence  Klf  K2,  K3,  K4,  in  the  asymmetric  carbon  atom,  the 
differences  between  Klf  K2,  K3,  K4,  giving  the  rotatory  power. 

Guye's  hypothesis  is  similar,  except  that  he  considers  the 
mass  of  the  groups  to  be  the  "influence".  This  theory  has 
proved  in  accordance  with  facts  in  a  number  of  series  and  at 
variance  with  facts  in  many  others.  Groups  of  equal  mass 
should  destroy  activity  were  mass  the  only  influence,  but  Guye 
8 


ii4         A  SHORT  HISTORY  OF  CHEMISTRY 

himself,  Purdie,  Walden  and  others  have  shown  that  compounds 
containing  two  different  groups  of  equal  mass  are  optically 
active.  It  may  be  remarked  that  this  discrepancy  would  dis- 
appear if  the  "  influences ''  were  assumed  to  be  forces  of  some 
kind  between  the  groups  and  the  asymmetric  atoms.  All  re- 
searches carried  out  on  the  quantitative  nature  of  optical 
activity  tend  to  show  it  to  be,  of  all  physical  properties,  that 
most  susceptible  to  constitutive  influences. 

(a)  Asymmetric  Synthesis. — Cohen  and  Whiteley  (1901)  made 
several  unsuccessful  attempts  to  form  active  acids  from  active 
esters  of  acids  containing  no  asymmetric  atom  (e.g.  lactic  from 
pyruvic,  etc.) ;  more  success  has  been  obtained  by  Marckwald 
and  McKenzie  (1901)  and  by  McKenzie  (1904-8),  who  has  ac- 
complished asymmetric  syntheses  of  mandelic,  lactic,  phenyl- 
methyl-glycollic  and  other  acids,  and  of  benzoin. 

Numerical  Relations  of  Optical  Activity. 

(a)  Homologous  Series. — The  work  of  Tschugaew  (1898), 
Guye  (1895),  and  others  shows  that,  on  ascending  the  normal 
series  of  aliphatic  acids  or  amines,  the  molecular  rotation  of 
optically  active  salts  or  esters  attains  an  approximately  constant 
value  after  the  first  few  members  of  the  series  have  been  passed. 

(ti)  Ring-formation. — It  has  long  been  known  that  anhydrides 
or  lactones  derived  from  active  acids  show  a  great  difference  in 
rotation  from  the  parent  substances,  and  that  substances  such  as 
boro-tartrates  (1890;,  probably  possessing  a  structure  such  as 

O— CH  .  COOH 

HO — B<^  show   greatly    enhanced   activity. 

XO— CH  .  COOH, 

Haller  and  Desfontaines  (1905)  have  found  the  same  on  for- 
mation of  active  methyl-cyclopentanone  derivatives  from  those 
of  active  /3-methyladipic  esters. 

(c)  Structural  and  Position-isomerism. — The  influence  of 
constitution  is  too  great  to  permit  of  any  definite  rules  being 


THE  HISTORY  OF  ORGANIC  CHEMISTRY      115 

formed  with  reference  to  ordinary  structure  isomers,  but  the 
effect  of  ortho-j  meta-  and /^^-substitution  clearly  depends  on 
the  nature  of  the  substituent  and  the  proximity  to  the  unsaturated 
group  (Tschugaew,  1898;  Cohen,  1905). 

(d)  Unsaturation  exerts  an  increasing  effect  on  optical  activity 
(Walden,  1896;   Klages  and  Sautter,   1904),   the  effect  being 
very   much   more   marked   when   two    unsaturated  groups    (a 
"conjugated"  system)  occur  together  (Haller,   1899;  Hilditch, 
1909). 

(e)  Activity  of  Electrolytes. — Landolt  (1873)  and  Oudemans 
(1879)  found  that  aqueous  solutions  of  mineral  salts  of  active 
acids  or  bases  possess,  when  sufficiently  dilute,  the  same  mole- 
cular rotation,  a  result  which,  as  Hadrich  (1893)  pointed  out, 
follows  from  the  ionic  theory,  the  constant  value  being  the 
rotation  of  the  optically-active  ion  concerned. 

(/)  The  phenomenon  of  Muta-rotation  has  been  known  for 
many  years  as  regards  the  sugars ;  it  has  already  been  referred 

to  (§  7)- 

(g]  The  Influence  of  Solvents  on  optical  activity  has  been 
very  thoroughly  examined  by  Patterson  (1900  and  onwards). 

Other  Elements  Obtained  in  the  Optically -active  State. — Un- 
successful attempts  have  been  made  to  resolve  asymmetric 
derivatives  of  quinquevalent  phosphorus  (Michaelis,  1901)  and 
arsenic  (Michaelis,  1902),  and  of  tervalent  iodine  (Kipping  and 
Peters,  1900).  The  following  elements  have  been  obtained  in 
optically-active  forms : — 

(a)  Nitrogen. — Le  Bel  (1891)  partially  resolved  /'-methyl- 
ethylpropylisobutyl-ammonium  chloride  biochemically;  Pope 
and  Peachey  (1899)  succeeded  with  r-a-phenylbenzylallylmethyl- 
ammonium  iodide.1 

1  The  quinquevalent  nitrogen  atom  has  been  conceived  as  acting  (i)  at 
the  centre  of  a  cube,  with  valencies  directed  to  5  of  the  angles  (van  't 
Hoff,  1878) ;  (ii)  at  the  centre  of  two  superposed  tetrahedra  (Willgerodt, 
1890) ;  (iii)  at  the  centre  of  a  tetragonal  pyramid  (Bischoff,  1890),  which, 
according  to  H.  O.  Jones  (1905),  best  accounts  for  the  changed  properties 


u6         A  SHORT  HISTORY  OF  CHEMISTRY 

(£)  Tin. — Methyl-ethyl-propyl  stannonium  salts  were  resolved 
by  Pope  and  Peachey  (1900). 

(c)  Sulphur. — Smiles  (1900)  resolved  N-methylethylphenacyl 
sulphonium  bromocamphorsulphonates  and  almost  simultane- 
ously Pope  and   Peachey  split   N-methylethylthetine  bromo- 
camphorsulphonate  into  its  active  components. 

(d)  Selenium  compounds  were  resolved  by  Pope  and  Neville 
(1902)  similarly  to  the  second  production  of  asymmetric  sulphur 
mentioned  above. 

(e)  Silicon  compounds,  such  as  ethylpropylbenzyl  silicol  and 
sulphonic  acids  derived  from  the  corresponding  silicol  oxide 
have  been  resolved  by  Kipping  (1904-8)  in  the  course  of  exten- 
sive work  on  the  organic  derivatives  of  silicon. 

on  alteration  of  tervalent  to  quinquevalent  nitrogen  ;  and  (iv)  at  the 
centre  of  a  regular  tetrahedron,  like  carbon,  the  fifth  valency  being  mobile 
and  of  no  definite  position. 


CHAPTER  VII 


COMPOUNDS  AND  REACTIONS  IN  ORGANIC 
CHEMISTRY 

As  we  remarked  in  a  previous  chapter,  historical  interest  at- 
taches rather  to  general  reactions  and  development  of  classifica- 
tion than  to  particular  substances,  and  so  in  dealing  with  the 
organic  side  of  the  science,  we  shall  try  to  indicate  the  lines 
along  which  synthetic  methods  have  developed,  the  chief  classes 
of  reactions  which  have  been  discovered,  and  the  chief  types 
of  compounds  formed  thereby. 

§  i.  Hydrocarbons— The  majority  of  the  hydrocarbons 
have  been  prepared  subsequently  to  their  more  important  de- 
rivatives, but  the  following  list  will  show  how  the  more  notable 
members  of  the  series  came  to  be  found  : — 

CH4  Methane  Known  to  van  Helmont.  First  synthesis 

(CSa  4-  H2S  over  Cu)  by  Berthelot,  1858. 

C.,H6  Ethane  1848  Frankland  (K  on  C2H5CN,  and  Zn 

(C2H5)2  +  H2O)  and  Kolbe  (electrolysis  of 
potassium  acetate). 

(1795  The  "  four  Dutch  chemists  ". 
1866  Tollens  (Na  on  C3H4C13). 
1868  Butlerow  (Cu  on  CH2I2  at  100°). 

C2H2       Acetylene  1836  Discovered  by   Edmund  Davy.     Syn- 

thesized by  Berthelot,  1863  (electric  arc  in 
hydrogen). 

C6HC      Benzene  1825  Faraday  (in  coal  gas) ;   1834  Mitscher- 

lich  (distilling  benzoic  acid  and  lime) ; 
1845  Hofmann  (in  coal-tar) ;  1870  Berthe- 
lot (synthesis  from  acetylene). 

C9H12     Mesitylene  1868  Fittig;  1838  Kane. 

Ci2H10    Diphenyl  1866  Berthelot. 

C19H16     Triphenylmethane     1872  Kekul6     (benzal     chloride  +  mercury 
diphenyl). 

117 


n8         A  SHORT  HISTORY  OF  CHEMISTRY 

Other  instances  have  already  been  given  in  Chapter  vi.  (cycloparaffins 
and  hydrocarbons  containing  conjugated  aromatic  nuclei). 

A  number  of  general  methods  of  synthesis  for  hydrocarbons 
have  been  devised  from  time  to  time.  Such  are : — 

Electrolysis  of  alkaline  salts  of  saturated  fatty  mono-  and  di-basic  and 
of  maleic  or  fumaric  acids  (Kolbe,  1848  ;  Kekule,  1864). 

The  action  of  sodium  on  alkyl  halides  (Wurtz,  1855). 

The  action  of  sodium  on  a  mixture  oi  an  alkyl  and  an  aryl  halide 
(Fittig,  1863). 

The  action  of  A1C13  on  an  aromatic  hydrocarbon  and  an  alkyl  halide 
(Friedel  and  Crafts,  1870). 

The  action  of  alcohol  on  diazo-bodies  (Griess,  1866). 

Polymerization  (acetone  to  mesitylene,  Kane,  1838  ;  diacetyl  to  p-xylo- 
quinone,  v.  Pechmann,  1889,  etc.). 

The  extensions  of  the  Friedel-Crafts  reaction  should  be 
noted  :— 

Preparation  of  silicon  derivatives  (Ladenburg,  1875). 

Preparation  of  aldehydes  and  ketones  from  acid  chlorides  and  benzenes 
(Gattermann,  1897). 

Preparation  of  sulphinic  acids  from  sulphur  dioxide  and  benzenes 
(Knoevenagel,  1908;  Smiles,  1908). 

Preparation  of  sulphonium  bases,  etc.,  from  sulphur  dioxide  and  phenolic 
ethers  (Smiles,  and  Le  Rossignol,  1908). 

The  preparation  of  hydrocarbons  by  reduction  has  been 
effected  in  numerous  instances,  of  which  Berthelot's  (fuming 
hydriodic  acid),  Baeyer's  (reduction  of  hydroxyl  groups  by  zinc 
or  by  phosphorus  and  hydriodic  acid),  and  the  recent  method 
of  passing  a  mixture  of  hydrogen  and  the  vapour  to  be  reduced 
over  heated  finely-divided  nickel  (Sabatier  and  Senderens)  are 
the  most  interesting. 

The  following  methods  for  the  synthesis  of  polymethylene 
derivatives  may  also  be  cited  here  : — 

The  action  of  sodium  on  dibromoparaffins  (Freund,  1882). 
The  action  of  iodine  or  alkylene  dibromides  on  disodium  derivatives  of 
malonic  esters  (W.  H.  Perkin,  jun.,  1894). 


COMPOUNDS  IN  ORGANIC  CHEMISTRY      119 

Elimination  of  nitrogen  from  aliphatic  diazo-compounds  (Buchner). 
Distillation  of  calcium  salts  of  the  fatty  dibasic  acids  (J.  Wislicenus, 

1893). 

Beilstein  (1880)  noted  that  Russian  petroleum  consisted  largely  of 
hexamethylenes  (naphthenes).  Crossley  has  contributed  to  the  recent 
knowledge  gained  on  the  subject  of  polymethylene  and  hydroaromatic 
derivatives. 

Finally,  we  must  refer  to  the  recent  work  of  Gomberg  (1900), 
Tschitschibabin,  and  others  on  "  triphenylmethyl  " ;  this  was  at 
first  thought  to  contain  tervalent  carbon;  other  explanations 
of  its  formation  and  reactions,  based  on  the  usual  assumptions 
of  the  valency  of  carbon,  have  since  been  put  forward. 

§  2.  Oxygen  Derivatives :  (a)  Hydroxylic  Compounds 
— The  chief  synthetic  methods  for  the  most  important  class  of 
hydroxyl  derivatives,  the  alcohols,  have  been  : — 

(#)  The  replacement  of  halogen,  etc.,  by  alkaline  hydroxyl. 

(b)  The  reduction  of  aldehydes  (Wurtz,  1866)  and  ketones 
(Friedel,  1862). 

(c)  The   extended   action   of  zinc  alkyls  on  acid  chlorides 
(Butlerow,  1864). 

(d)  The  action  of  magnesium  alkylhalides  on  carbonyl  oxygen 
(Grignard,  1900). 

On  p.  1 20  we  summarize  the  history  of  the  more  noteworthy 
alcohols  and  phenols. 

Another  section  of  oxygen  derivatives  closely  allied  to  the 
true  hydroxylic  compounds  is  that  of  the  ethers.  The  substance 
which  we  now  call  diethyl  ether  was  known  as  ether,  or  sulphur 
ether,  to  the  alchemists,  and  its  preparation  from  alcohol  and 
sulphuric  acid  is  referred  to  by  the  later  alchemists  and  the 
phlogistic  chemists.  The  name  ether  was  applied  on  account 
of  the  volatile  properties  of  the  liquid,  and  other  liquids  subse- 
quently discovered,  and  possessing  a  similar  odour  to  ether, 
were  also  indiscriminately  termed  ethers.  We  have  already  seen 
(chap,  vi.)  that  much  of  the  discussion  on  organic  theory  in  the 
earlier  years  of  the  modern  era  centred  round  alcohol  and  ether, 


120          A  SHORT  HISTORY  OF  CHEMISTRY 


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COMPOUNDS  IN  ORGANIC  CHEMISTRY      121 

and  in  consequence  of  this  the  distinction  between  "  simple  " 
ethers  and  "compound"  ethers  (later  called  esters)  was  soon 
observed.  We  may  recall  at  this  point  how  Williamson  (and, 
independently,  Chancel)  finally  solved  the  problems  of  the  con- 
stitution of  ether  and  of  its  production  by  the  sulphuric  acid 
process,  showing  at  the  same  time  how  "  mixed  "  "  simple  "  ethers 
of  the  type  R — O — R1  could  exist.  The  anaesthetic  properties 
of  ether  were  discovered  by  Jackson  (1842).  Mention  may 
also  be  made  of  the  class  of  phenolic  ethers,  of  which  anisol, 
C6H4OCH3  (discovered  by  Cahours,  1841),  may  be  taken  as 
typical.  The  discovery  of  some  characteristic  esters  is  recalled 
in  the  following  table  : — 

Ethyl  acetate  1759  Lauroguais. 

,,     chlorcarbonate  1833  Durnas  (phosgene  and  alcohol). 

Ethylene  dichloride  1795  Four  Dutch  chemists  (ethylene  +  C12). 

„        dibromide  1826  Balard  (ethylene  +  Br2). 

,,        di-iodide  1821  Faraday  (sunlight  on  ethylene  +  I2). 

Chloroform  1831  Liebig;  Soubeiran,  1847,  used  in  sur- 

gery (Simpson). 

lodoform  1832  Serullas. 

Ethyl  hydrogen  sulphate      ( 1833-40  Hennel,     Serullas,     Magnus    and 

and  ethionic  acids  1  Regnault. 

Ethyl  hydrogen  phosphate     1833  P£louze. 

„  „          carbonate     1840  Mitscherlich. 

Glyceryl  trinitrate  1847  Sobrero  ("  nitro-glycerine  "). 

(The  products  of  the  action  of  HNO,  on  ethyl  alcohol  were  studied  by 
Debus,  1856.) 

§  3-  Oxygen  Derivatives :  (8)  Carbonyl  Compounds, 
Reactions  of  Condensation — Aldehydes  and  ketones  have 
been  prepared  chiefly  by  the  oxidation  of  alcohols  (Scheele, 
1774),  the  distillation  of  calcium  salts  of  fatty  acids  (William- 
son), the  action  of  zinc  alkyls  on  acid  chlorides  (Freund,  1860), 
Gattermann's  aluminium  chloride  reaction  (cf.  p.  118)  and 
Grignard's  reaction  (1900;  the  action  of  magnesium  alkyl 
halides  on  form-alkylanilides,  formic  ester,  and  iso-nitriles 
(aldehydes)  and  on  nitriles  and  amides  (ketones)).  The 


122         A  SHORT  HISTORY  OF  CHEMISTRY 

detection  of  the  carbonyl  group  has  been  effected  by  hydroxy- 
lamine  (oximes,  V.  Meyer,  1882)  and  phenylhydrazine  (E. 
Fischer,  1877).  The  development  of  a  series  of  "condensa- 
tion reactions "  of  aldehydes  and  ketones  (reactions  accom- 
panied by  elimination  of  the  elements  of  water  or  alcohol)  may 
here  be  dealt  with  : — 

(a)  The  aldol  condensation  of  aldehydes  or  ketones  in  presence  of  acid 
or   alkali,   e.g.    CH3CHO  +  CH3  .  CHO  _>  CH3  .  CH(OH)  .  CH2 .  CHO 
(aldol)  ->  CH3.  CH  :  CH .  CHO  (crotonaldehyde).   Wurtz  (1872)  studied 
this  particular  case,  but  in  1866  Baeyer  had  observed  the  similar  forma- 
tion of  mesityl  oxide  and  phorone  from  acetone. 

(b)  The  benzoin   condensation   first   noticed  by   Liebig   and  Wohler 
(1832)  in  the  action  of  KCN  on  benzaldehyde,  but  only  satisfactorily 
explained  by  Lapworth  in  1903. 

(c)  The  Claisen  condensation  of  carbonyl  derivatives  with  substances 
containing  the  keten  group — CH2 — CO — ;  examples  of  compounds  so 
formed  are  benzalacetone  (Claisen,  1881) ;  o-nitrobenzalacetone  (Baeyer, 
1882 ;  used  in    indigo-synthesis),  cinnamalacetone  (Einhorn  and  Diehl, 
1885),  a-acrose  (dl-fructose)  (E.  Fischer,  1887,  from  formaldehyde),  and 
ionone  (Tiemann,  1893,  from  citral). 

The  historically  noteworthy  members  of  this  group  appear  on 
the  opposite  page. 
§  4.  Oxygen  Derivatives :   (c)  Carboxylic  Acids — The 

importance  of  this  class  for  the  determination  of  constitution 
and  other  problems  is  obviously  very  great,  and  consequently 
a  very  large  number  of  syntheses  have  been  devised  ;  we  have 
only  space  to  refer  to  a  few,  such  as  oxidation  of  alcohols  or 
aldehydes,  saponification  of  nitriles  [Dumas  and  Frankland  and 
Kolbe  (1847),  acetoacetic  and  malonic  ester  syntheses  (cf.  §  5), 
and  metal-alkyi  syntheses  (Na  +  CO2  +  C6H5Br,  Kekule,  1866  ; 
finely-divided  silver  on  halogen  fatty  acids,  J.  Wislicenus,  1868  ; 
zinc  on  chloracetic  and  oxalic  esters,  Fittig  and  Daimler,  1887  ; 
zinc  on  ketones  and  iodacetic  esters,  Reformatski,  1887,  used 
in  synthesis  of  citric  acid,  Lawrence,  1897) ;  Grignard  reaction]. 
Perkins'  reaction  for  the  preparation  of  ethylenic  acids  by  heat- 
ing a  mixture  of  aldehyde,  sodium  fatty  acid  salt  and  acid 


COMPOUNDS  IN  ORGANIC  CHEMISTRY       123 


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i24         A  SHORT  HISTORY  OF  CHEMISTRY 

anhydride  (1868,  coumaric ;  1875,  cinnamic  acid)  has  been 
studied  in  addition  by  Baeyer,  Conrad,  Fittig,  and  others,  but 
its  precise  mechanism  is  not  quite  definitely  understood.  In  the 
course  of  his  work  Fittig  was  able  to  shed  much  light  on  the 
constitution  of  lactones  (paraconic  acids,  1894-1904),  and  to 
confirm  the  ideas  put  forward  by  Erlenmeyer,  sen.  (1880),  to 
account  for  Saytzew's  butyrolactone  (1873)  and  Bredt's  isocapro- 
lactone  (1880). 

The  structure  of  amido-acids  (see  also  chap,  viii.)  was  defined 
when  Perkin  and  Duppa  obtained  glycocoll  (already  prepared 
from  glue  (Braconnot,  1820),  hippuric  acid  (Dessaignes,  1846), 
and  bile  (Strecker,  1848))  by  the  action  of  ammonia  on  bromo- 
acetic  acid  in  1858,  and  that  otoxy-acids  followed,  since  glycocoll 
had  been  submitted  to  the  action  of  nitrous  acid  (Strecker,  1848). 
The  latter  have  also  been  prepared  by  the  action  of  zinc  alkyl 
halides  on  oxalic  ester  (Frankland  and  Duppa,  1865),  from 
aldehyde  cyanhydrins  (Wislicenus,  1862)  and  from  Grignard's 
reagent  and  ketonic  esters  (McKenzie,  1905). 

The  first  nitrites  to  be  prepared  seem  to  have  been  proprio- 
nitrile  (1834,  Pelouze,  Ba(C2H5)SO4  +  KCN),  aceto-nitrile  (1847, 
Dumas,  phosphoric  anhydride  and  ammonium  acetate)  and 
benzonitrile  (1844,  Fehling).  With  the  anhydrides  (Gerhardt, 
1852)  may  be  mentioned  the  acid  peroxides  (Brodie,  1864, 
from  the  former  and  BaO2).  Various  improvements  have  been 
made  in  the  preparation  of  acid  chlorides  since  Liebig  and 
Wohler  produced  the  first  member  in  1832  by  the  chlorination 
of  benzaldehyde,  such  as  the  interaction  of  the  sodium  salts 
with  phosphorus  pentachloride  (Cahours,  1846),  trichloride 
(Bechamp,  1856),  oxychloride  (Gerhardt,  1851),  or  thionyl 
chloride  (Hermann,  1883).  Reference  must  finally  be  made  to 
the  amides,  such  as  oxamide  (from  ammonium  oxalate,  Dumas, 
1830  ;  ammonia  and  oxalic  ester,  Liebig,  1834),  benzamide 
(ammonia  and  benzoyl  chloride,  Liebig  and  Wohler,  1832), 
acetamide  (Dumas,  1847)  and  the  anilides  (Gerhardt,  1845). 

Details  of  interest  are  connected  with  the  following  acids  ; — 


COMPOUNDS  IN  ORGANIC  CHEMISTRY      125 


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126         A  SHORT  HISTORY  OF  CHEMISTRY 

§  5-  Oxygen  Derivatives :  (d)  Ketonic  Acids — This  sec- 
tion of  the  organic  acids  is  particularly  important,  because  many 
of  its  members  (all  those  possessing  the  group  — CH.,  -  CO — ) 
are  able,  by  virtue  of  the  acidic  properties  of  the  methylene 
hydrogen  atoms,  to  enter  into  all  manner  of  complex  synthetic 
reactions.  The  following  are  typical : — 

(a)  Action  of  chlorcarbonic  esters  on  the  sodium  compounds  of  aceto- 
acetic  ester,  malonic  ester,  etc.  (1877  Conrad;  1882-6  Bischoff;  in    1879 
Conrad  undertook  a  comprehensive  investigation  of  the   malonic   ester 
syntheses,  foreshadowed  by  van  't  Hoff  in  1874). 

(b)  Action  of  iodine  on  the  sodium  compounds  (dioxysuccinic  esters, 
Bischoff,  1884). 

(c)  Action  of  alkylene  bromides  on  the  sodium  compounds  (Bischoff, 
1 880-8 ;  Perkin,  jun.,  1902). 

(d)  Condensation   of    phenanthraquinone    and    acetoacetic    ester    by 
ammonia  (Japp  and  Streatfield,  1883). 

(c)  Condensation  of  aldehydes  and  acetoacetic  ester  by  organic  bases 
(Knoevenagel's  reaction,  1893). 

(/)  Condensation  of  olefinic  or  acetylenic  esters  with  sodium  compounds 
of  acetoacetic,  malonic,  or  cyanoacetic  esters  (Michael's  reaction,  1887). 

(g)  Condensation  of  hydrazines,  etc.,  and ketonic  esters,  yielding  hetero- 
cyclic  bodies  (cf.  §  8). 

The  parent  member  of  the  polyketides>  as  Collie  (1907)  has 
proposed  to  term  substances  containing  the  — CH2 .  CO —  group, 
is  keten  CH2 :  CO,  isolated  by  Wilsmore  and  Stewart  (1907) ; 
substituted  ketens  have  been  prepared  by  Staudinger  from 
bromacyl  bromides  and  zinc,  while  a  new  oxide  of  carbon, 
carbon  suboxide  C3O2,  prepared  by  distilling  malonic  ester  and 
phosphoric  anhydride  (1906,  Diels  and  Wolf),  appears  to  be  a 
keten  derivative,  CO  :  C  :  CO.  Acetylketen  is  a  polymer  of 
keten,  and  an  internal  anhydride  of  acetoacetic  acid  (Chick 
and  Wilsmore,  1908). 

Typical  ketonic  acids  are  : — 

CH3.CO.COOH  Pyruvic;  obtained  by  iatro-chemists  in  distilling 
"  tartar,"  and  by  Berzelius  (1835). 

CH3CO  .  CH2 .  COOH  Acetoacetic  (referred  to  in  chap.  vi.). 
CH3CO .  CH2 .  CH2 .  COOH  Laevulinic ;  1874  v.  Grote  and  Tollens. 


COMPOUNDS  IN  ORGANIC  CHEMISTRY      127 

CO(CH2 .  COOH)2  Acetonedicarboxylic ;  1884  v.  Pechmann  (from  citric 
acid). 

C6H5.  CO  .  CHa  .  COOH  Benzoylacetic  :  1884  Perkin  (phenyl-propiolic 
and  strong  sulphuric  acid)  ;  1887  Claisen  (condensation  of  benzoic  and 
acetic  esters). 

§  6.  Nitrogen  Derivatives — These  have  been  very  fully 
studied  during  the  past  century,  since  the  constitution  of  so 
many  vegetable  and  animal  products,  as  well  as  the  preparation 
of  dyes,  explosives  and  other  technically  valuable  substances 
depends  on  the  function  of  the  nitrogen-containing  group. 

Commencing  with  nitro-compounds  (the  first  of  which,  ex- 
cluding picric  acid,  was  nitrobenzene,  Mitscherlich,  1834),  we 
notice  the  evolution  of  methods  of  nitration  in  the  aromatic 
series,  and  the  preparation  of  the  first  aliphatic  members  by 
Kolbe  and  by  V.  Meyer  in  1872.  The  latter  extended  his 
studies  to  the  conversion  of  nitre-paraffins  to  nitrols,  nitrolic 
acids,  etc.  Nitroso  compounds  were  obtained  by  the  action 
of  mercury  diphenyl  and  nitrosyl  bromide  (Baeyer,  1874),  and 
of  nitrous  acid  on  secondary  amines  and  on  phenols  (Baeyer 
and  H.  Caro,  1874,  1874). 

The  flw/dfo-derivatives  form  the  most  important  class  of 
nitrogen  compounds.  Aliphatic  amines  have  been  prepared 
by  intraction  of  alkyl  isocyanates  and  caustic  potash  (Wurtz, 
1848),  alkylation  of  ammonia  (Hofmann,  1849),  reduction  of 
nitriles  (Mendius,  1862),  and  hydrolysis  of  isonitriles  (Hof- 
mann, 1868);  Hofmann  (1885)  also  illustrated  the  conversion 
of  amides  (by  bromine  and  potash)  to  the  next  lower  amine. 
Besides  Hofmann's  alkylation  of  aniline,  aromatic  amines  have 
been  prepared  by  reduction  of  nitro-compounds  by  ammonium 
sulphide  (Zinin,  1841),  hydrochloric  acid  and  zinc  (Hofmann, 
1845),  iron  (Bechamp,  1852)  or  tin  (Roussin),  and  electrolytic- 
ally  (Lob,  1900).  The  electrolytic  reduction  of  nitrobenzene, 
in  particular,  has  led  under  suitable  conditions  to  methods  for 
the  preparation  of  azoxy-,  azo-,  hydrazo-,  or  amino-benzene. 
The  following  individual  amines  and  related  derivatives  are 
worthy  of  note  : — 


128         A  SHORT  HISTORY  OF  CHEMISTRY 

Aniline  (1826  Unverdorben,  distillation  of  indigo  ;  1834  Runge, 
"  cyanol  "  in  coal-tar  ;  1841  Fritzsche,  "  aniline,"  from  indigo  and  potash  ; 
1841  Zinin,  reduction  of  nitrobenzene  —  all  four  substances  proved  identical 
by  Hofmann,  1843)  ;  p-toluidine  (1845,  Hofmann)  ;  diphenylamine  (1864, 
Hofmann,  from  rosaniline)  ;  azoxybenzene  (Mitscherlich,  1834)  ;  hydrazo- 
benzene  (Hofmann,  1863),  which  changes  so  readily  to  the  isomeric  ben- 
zidine  (already  obtained  by  Zinin  in  1845  by  acid  reduction  of  azo-benzene, 
the  intermediate  hydrazo-compound  being  overlooked)  ;  and  a-  and  /3- 
naphthylamines  (Zinin,  1842;  Liebermann,  1876).  The  constitution  of 
the  numerous  intermediate  reduction  products  of  nitrobenzene  is  mainly 
due  to  Erlenmeyer  and  Kekule*. 

The  derivatives  of  hydrazine  belong  here  and  include  phenyl- 
hydrazine  (E.  Fischer,  1875,  who  obtained  it  from  potassium 
phenylhydrazine  sulphonate,  previously  prepared  by  Strecker  in 
1871),  and  the  alkylhydrazines  (E.  Fischer,  1879). 

Other  amino-compounds  are  :  — 

CO(NH2)2  Carbamide          1773  Rouelle   (in   urine)  ;    1828  Wohler  (from 

ammonium  cyanate). 

C(NH)(NHa).,  Guanidine    1861  Strecker  (oxidation  of  guanine). 
CN  .  NH2  Cyanamide         1838  Bineau   (CNC1  +  NH3);    recently  intro- 

duced as  a  manure. 

The  first  diazo-compounds  were  obtained  by  Griess  in  1863 
from  aniline;  the  problem  of  their  constitution  has  already 
been  discussed  (ch.  vi.  §  7).  The  discovery  of  diazo-amido- 
benzene  and  its  conversion  to  amido-azobenzene  (Griess,  1862) 
was  of  great  importance  to  the  dyeing  industry.  Other  in- 
teresting diazo-bodies  are  :  — 

/N 
C6H5.N^       Diazoimidobenzene  1866  Griess. 


^    ||  Di 


CH3          Diazomethane 


CO2C3H5  .  CHN2  Diazoacetic  ester         1883  Curtius    (nitrous    acid    and 

glycocoll). 

CH3  .  N  =  N  .  NH  .  R  Aliphatic  diazo-/igo7  Dimroth  (Grignard  reagent 
amido  compounds  \  and  diazo-paraffins). 

There  remain,  in  conclusion,  the    isonitriles   (predicted  by 
Kolbe,  and  discovered  at  about  the  same   time  by  Gautier 


COMPOUNDS  IN  ORGANIC  CHEMISTRY      129 

(alkyl  iodides  and  silver  nitrate)  and  Hofmann  (chloroform, 
primary  amine,  and  alkali)  in  1866),  and  the  isonitroso  com- 
pounds, including  the  oximes  (Victor  Meyer,  1883  and  the 
compounds  formed  by  the  action  of  nitrous  acid  (or  amyl 
nitrite)  on  the  methylene  group  — CH2 — -  under  suitable  con- 
ditions (V.  Meyer,  1882). 

Other  nitrogenous  compounds  will  be  mentioned  in  cort^ 
nexion  with  the  history  of  alkaloids,  proteins,  dyestuffs,  etc* 

§  7.  Derivatives  of  Elements  other  than  Oxygen  or 
Nitrogen — The  researches  in  this  direction  group  themselves 
into  three  main  classes  : — 

(a)  The  study  of  compounds  analogous  to  the  amines. 

(b)  The  study  of  sulphur  compounds. 

(c)  The  study  of  "  organo- metallic  "  derivatives. 

(a)  To  this  section  belongs  the  work  on  the  alkyl  derivatives  of  phospho- 
rus, arsenic,  and  antimony.     Aliphatic  tertiary  phosphines  were  discovered 
by  The'nard  in  1846  (from  alkyl  iodides  and  calcium  phosphide),  while  Hof- 
mann prepared  the  primary  and  secondary  bases  by  his  alkylation  method 
in  1871.     Aromatic  phosphines  (C6H5PH3,  C6H5PO2  and  C6H5P  :  PC6H5) 
were  derived  by  Michael  in  1876  from  C6H5PC12.     Tertiary  and  quater- 
nary arsenic   and  antimony  compounds  have  been  chiefly  studied  by 
Lowig  and  Landolt  (1853) ;  the  primary  and  secondary  arsenic  derivatives 
were  found  to  be  non-basic,  the  primary  (mono-methyl)  bodies  being  due 
to  Baeyer  (1858).     The  secondary  compounds  are  of  especial  interest,  for 
they  form  one  of  the  three  "  pillars  "  of  the  older  radical  theory,  and  were 
studied  much  earlier  than  any  of  the  others.     They  were  investigated  by 
Bunsen  (1837-43),  who  isolated  many  derivatives  of  "  cacodyl  "  (CH3)aAs — 
from  "  Cadet's  fuming  arsenical  liquid,"  first  prepared  in  1760  by  Cadet 
by  distilling  arsenious  acid  and  potassium  acetate. 

(b)  Organic  sulphur  compounds  have  been  found  to  contain  bi-,quadri-, 
or  sexa-valent  sulphur,  and  while  the  bi-  and  sexa-valent  compounds  are 
now  well  defined  there  is  still  room  for  improvement  in  our  knowledge  of 
the  behaviour  of  many  substances  containing  quadrivalent  sulphur. 

The  bi-valent  derivatives  include  the  mercaptans  and  sulphides  (C3H5SH, 
discovered  by  Zeise,  1834;  (C3H5)2S,  allyl  sulphide,  isolated  from  garlic  by 
Wertheim,  1844 ;  C6H5SH,  Kekule,  1867) ;  derivatives  of  thiocarbonic  acid 
(CS2,  Lampadius,  1796,  from  pyrites  and  coal;  COS,  v.  Than,  1867; 
xanthates  RO.CS.SK,  Zeise,  1824,  from  CS2,  alcohol  and  soda); 
CS(NH2)3  thiourea,  Reynolds  (1869,  from  NH4CNS) ;  thioacetic  acid 
9 


130         A  SHORT  HISTORY  OF  CHEMISTRY 

CH3  .  COSH,  Kekule,  1854  5  ancl  the  mustard  oils  (alkyl  isothiocya  nates, 
R  .  N  :  C  :  S)  of  which  allyl  isothiocyanate  (in  mustard  seeds)  was  the 
first  to  be  isolated  (Bussy,  1840),  and  whose  constitution  and  synthesis 
were  worked  out  by  Hofrriann  about  1868. 

The  most  interesting  quadrivalent  sulphur  compounds  are  the  sulphinic 
acids  (aliphatic,  1857,  Hobson  ;  aromatic,  1862,  Kalle),  sulphoxides  (1866, 
Saytzew)  and  sulphonium  bases  (aliphatic,  1865,  Cahours  ;  aromatic, 
Smiles  and  Le  Rossignol,  1906).  Thionyl  derivatives  of  amines,  R  .  N  :  SO, 
have  been  studied  by  Michael  (1891).  It  is  probable  that  the  constitu- 
tion of  not  a  few  dyestuffs  containing  sulphur  will  be  shown  to  depend 
upon  the  presence  of  quadrivalent  sulphur. 

The  sexavalent  derivatives  are  perhaps  the  best  known,  such  as  the 
tmlphonic  acids  (methylsulphonic,  Kolbe,  1845,  benzene  sulphonic,  Mits- 
cherlich,  1833  ;  sulphanilic  (p-aminobenzenesulphonic),  Gerhardt,  1845  (sul- 
phonation  of  aniline)  ;  and  the  many  dyes  which  are  used  in  the  form  of 
sulphonic  acids  for  the  sake  of  superior  solubility),  and  the  sulphones 
(Saytzew,  1867  ;  a-disulphones  R  .  SO2  .  SO,R,  Kohler  and  Macdonald, 
1899,  and  Hilditch,  1908;  sulphonal  (CH3)2C(SO2C2H5)2  discovered  by 
Baumann  (1888),  and  applied  as  a  soporific  by  Kast  (1889)  ;  saccharin 

.  >so'\ 

C6H4  <^  /NH,  discovered  by  Remsen  and  Fahlberg  (1879)   in  the 

XCO/ 

alkaline  oxidation  of  o-toluene  sulphonamide). 

(c)  The  organic  compounds  of  silicon  have  proved  interesting  since 
Wohler  in  1863  showed  their  close  analogy  to  the  corresponding  carbon 
derivatives,  and  the  chief  workers  have  been,  for  the  aliphatic  compounds, 
Frankland  (zinc  alkyls  and  SiCl4)  and  Friedel  and  Crafts  (1863)  ;  for  aro- 
matic derivatives,  Ladenburg  (C6H5SiCl3,  1874)  and  Polis  ((C6H5)4Si,  1886). 
Kipping  has  recently  prepared  many  new  silicon  derivatives  by  the  action 
of  different  magnesium  alkyl  iodides  on  silicon  tetrachloride  (1907). 

Alkyl  compounds  of  other  metals  followed  chiefly  upon  Frankland's 
discovery  of  zinc  ethyl  in  1849,  and  were  prepared  from  the  zinc  alkyls 
and  metal  chlorides,  e.g.  tin  (Lowig,  1852,  Cahours,  1860)  ;  lead  (Pb(C2H5)4, 
Buckton,  1859).  Mercury  alkyls  were  made  from  sodium  amalgam  and  the 
alkyl  iodides  (Frankland,  1864  ;  Hg(C6H5)2,  Otto  and  Dreher,  1870). 

The  zinc  alkyls  are  exceedingly  difficult  to  manipulate,  and  Fleck  (1893) 
found  the  magnesium  compounds  even  worse  ;  Barbier,  however,  found  that 
a  mixture  of  finely-divided  magnesium  and  methyl  iodide  acted  readily  and 
with  the  same  result  as  the  alkyl  derivative  (1899),  and  in  1900  Grignard 
made  an  extensive  study  of  the  reaction  between  magnesium  and  alkyl 


\ 
halides,  showing  how  the  compounds  formed  (  Mgf        J  could  be  used 


COMPOUNDS  INORGANIC  CHEMISTRY      131 

in  all  manner  of  syntheses  (Grignard's  reagent).  Pfeiffer  has  applied  the 
reagent  to  various  metallic  chlorides  and  has  obtained  in  this  way  alkyl 
derivatives  of  mercury,  thallium,  bismuth,  platinum  and  other  metals. 

§  8.  Heterocyclic  Compounds — Dozens  of  ring-systems 
consisting  of  carbon,  oxygen,  sulphur  and  nitrogen  atoms  have 
been  synthesized  within  the  last  forty  years,  and  historical  data 
of  the  chief  members  of  these  have  already  been  furnished 
(chap.  vi.  p.  91) ;  it  remains  to  give  some  idea  at  this  point  of 
the  manner  in  which  the  methods  of  synthesis  of  the  various 
types  have  developed,  and  we  may  confine  our  attention  to  the 
five-  and  six-membered  rings,  the  rest  being  relatively  unim- 
portant. The  synthetic  reactions  may  be  grouped  as  follows  : — 

I.  Pyrogemtic  reactions  : — 


Carbazole  |  j    (Grabe,  1873;   from  diphenylamine). 

NH 

S 


Thiodiphenylamine  [Til    (Bernthsen,  1888  ;    diphenylamine 

and  sulphur). 


.N— C. 


Pyrimidines  C 


X 


NH 


:C  (E.  v.  Meyer,  1889 ;  polymerization  of  nitriles) 


^N— CT 
II.  Reduction  reactions  : — 

CH 
Indol    |         |        CH  (Baeyer,  1869;  from  o-nitrocinnamic  aldehyde). 

\x 

NH 

CH 

,/\ 
Indazoles   j         j        NH  (Nolting,  1890;  from  o-nitro  compounds) 

\/ 

N 


132 


A  SHORT  HISTORY  OF  CHEMISTRY 


N 

/\x\ 

Benzimidazoles     |          |         CH  (Hobrecker,  1872  ;  from  o-nitro  compounds). 


NH 


O 


Benzoxazoles    |         j          CH  (Hubner,  1881 ;  from  benzoyl-y-nitrophenols). 


Quinoxalines 


(Hinsberg,  1896  ;  from  tf-nitrophenyl-a-amido-acids). 


N 


III.   Oxidation  reactions  :  — 

N 


Phenazines 


i886;  from  o-diamines  and  a-naphthol). 


N 


Quinolines    |         |         |     (Skraup,  1880 ;  from  anilines  and  glycerol). 

N 
IV.    Condensation  reactions  (a)  from  a.-diketones  : — 


C=C 


\ 


Glyoxalines     I     r//N  (Rodziszewski,  1882  ;  with  ammonia  and  aldehydes). 


Dihydropyrazines  (Weil,  1900  ;  with  alkylene  diamines). 

CH2\/CH 

N 


N 


Quinoxaline    I 


(Hinsberg,  1887  ;  with  o-diamines). 


COMPOUNDS  IN  ORGANIC  CHEMISTRY  133 

(b)  from  ft-diketones  : — 

x\ 

Pyridines     |          |    (Hantzsch,  1882 ;  with  aldehyde  ammonia). 


N 

/\/    \ 
Quinolines   |         j          |    (Knorr,  1886  ;  anilides  of  /3-keto-acids). 


N 


c/\c 

Pyrimidines  (Pinner,  1893  ;  with  acid  amidines). 

N\/N 
C 

Coumarones     (         |         |    (Hantzsch,  1886 ;  chloroacetoacetic  ester  and  phenates). 


O 


(c)   from  y-diketones  : — 


Furfuranes 


\/ 
O 


(Paal,  1885;  elimination  of  water). 


I         I 
Thiophenes    j         j    (Paal,  1885  ;  with  phosphorus  pentasulphide). 

\x 


s 


I       I 

Pyrrols    |         |    (Paal,  1885 ;  with  ammonia). 

V  X 


NH 


I  I 

Thiophenes    |         |    (Volhard  and  Erdmann,  1885 ;  sodium  succinate  and  PaS,). 

\x 


S 
(d)  from  o-diamines : — 

N 
\/\ 


/\/\ 

Benzimidazoles   |  CH  (Ladenburg,  1875  ;  with  fatty  acids). 

\    /\    / 


NH 


134 


A  SHORT  HISTORY  OF  CHEMISTRY 

N 
Quinoxaline    |  j    (Hinsberg,  1887  ;  with  cyanogen). 


N 
N 


Phenazine    | 


|    (Hinsberg,  1896  ;  with  o-quinones  or  pyro-catechol). 


(e)  from  o-aminophenols : — 
O 


Benzoxazoles 


Phenoxazine 


C  .  R  (Ladenburg,  1877  ;  with  fatty  acids), 


I          I    (Bernthsen,  1887  ;  with  pyrocatechol). 

\/\/ 


(/)  from  amino-aldehydes  or  ketones : — 


N  =CHx 

Oxazoles      I  )O  (Blumlein,  1884  ;  ct-chlorketones  and  amides). 

HC— CH/ 


Pyridine  |         J    (Schiff,  1861 ;  aldehyde-ammonia  and  aldehydes). 

V 


Quinoline    | 


Pyrazine 


N 


(Friedlander,  1883  ;  o-aminobenzaldehydes  and— CH2.  CO— 
compounds). 


(Skraup,  1893  ;  aminoaldehydes  and  aminoketones). 


N 


(g)  from  ammo-acids  ; — 
Pyridine 


|         (    (Bottinger,  1881 ;  from  gl 


utaconamic  acid). 


COMPOUNDS  IN  ORGANIC  CHEMISTRY  135 

Acridine    I         |  |         |    (Bernthsen,  1884  ;  from  diphenylamine  and  acids). 


N 
(/i)  from  hydrazine  and  hydroxylamine  : — 


Indol     I  |    (E.  Fischer,  1886 ;  from  certain  phenylhydrazones). 

\/\x 

NH 

Pyrazoles        |  /NH  (Claisen,  1888 ;  hydrazines  and  j8-diketones). 

HC  =  N    / 

Pyrazolones   CO^  |    (Knorr,  1883  ;  phenylhydrazjne  and  )8-ketonic  esters). 

CH 


Indazoles     | 


I   NH  (Fischer   and  Tafel,  1885;   from  o-hydrazine  cinna- 
mic  acids). 

N 


Triazoles    |  )NH  (Andreocci,  1892;  acid  hydrazides  and  amides). 


Isoquinoline  (Bamberger,  1894  ;  from  cinnamaldoxime). 

\/\/N 
(/)  Per  kin  s  reaction  : — 

Coumarin  (a-Pyrone)     |          |         |       (Perkin,  1865 ;  from  salicylaldehyde  and  acetic 
\/\/CO          anhydride). 
O 

(/)  Alkaline  condensation  or  decomposition  : — 


Coumarone    |         |          |    (Fittig,  1883  ;  from  coumarin  (loss  of  CO) ). 

O 
CO 


Isatin    I         |         CO    (Baeyer,  1880;  alkalies  on  o-nitrophenylpropiolic  acid). 

\/\/ 

NH 


136          A  SHORT  HISTORY  OF  CHEMISTRY 

Other  points  of  interest  which  may  be  chosen  from  the  history 
of  the  heterocyclic  group  are : — 

(a)  The  furfurane,  thiophene  and  pyrrol  compounds,  which 
present  so  close  an  analogy  to  the  benzene  and  pyridine  de- 
rivatives in  many  ways,  although  this  relation  and  the  cognate 
relationships  of  coumarone,  indol,  carbazole,  etc.,  to  the  three 
first-named   bodies  were  not  generally  recognized  till  about 
1885. 

(b)  The   connexion  found  to  exist  between  a  large  number 
of  natural  products,  notably  certain  vegetable  dyes  (quercetin , 
fisetin,  etc.),  and  the  y-pyrone  compounds 

CO 

/\ 

pyrone          ||      <||,  benzopyrone    |         |  and 

\/ 


\, 

c 


xanthone      | 


which  have  been  the  subject  of  study  by  Kostanecki,  A.  G. 
Perkin,  and  others  of  recent  years. 

(c)  The  importance  of  many  derivatives  of  pyridine,  quinoline 
and  ispquinoline  (especially  the  carboxylic  acids)  for  the  deter- 
mination of  the  constitution  of  the  alkaloids,  most  of  which 
yield  on  rupture  of  their  complicated  molecules  one  or  more 
of  these  simple  decomposition-products. 


CHAPTER  VIII 
THE  CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE 

§  i.  Chemical  Processes  in  the  Vegetable  and  Animal 
Kingdoms — Although  many  of  the  alchemists  professed  to 
regard  their  science  as  being,  by  reason  of  its  connexion  with 
the  process  of  life,  too  sacred  and  mysterious  for  the  average 
person  to  understand,  there  came  a  time  when  botanists  and 
physiologists  were  inclined  to  disparage  the  utility  of  any 
chemical  explanation  of  vital  processes,  holding  that  these  were 
caused  by  a  "  vital  force  "  of  a  nature  entirely  different  to  the 
ordinary  inorganic  "chemical  affinity".  In  spite  of  all  the 
chemical  work,  such  as  Lavoisier's  analyses  of  typical  organic 
bodies  and  Wohler's  or  Kolbe's  syntheses  of  organic  from  in- 
organic materials  tending  to  prove  that  there  was  nothing  chemi- 
cally anomalous  about  an  organic  compound,  this  opinion  held 
general  sway  until  about  the  middle  of  the  nineteenth  century. 
Perhaps  it  is  partly  in  consequence  of  this  that  the  first  modern 
investigations  on  the  chemical  reactions  going  on  in  plant  or 
animal  life  were  undertaken  in  most  cases  by  chemists  rather 
than  physiologists.  In  this  way  Fourcroy,  Vauquelin,  and 
later,  Berzelius,  studied  animal  chemistry,  while  Senebier,  Dutro- 
chet  and  especially  Saussure  worked  out  the  conditions  under 
which  carbonic  acid  is  absorbed  and  the  carbon  assimilated  by 
plants,  noting  that  certain  parts  of  plants  evolve  instead  of  ab- 
sorbing the  gas  and  that  a  small  evolution  of  heat  also  takes  place, 
thus  forming  an  analogy  with  animal  breathing. 

One  of  the  important  problems  in  both  plant  and  animal 
realms  is  nutrition,  and  the  chemical  nature  of  the  subject  be- 


138         A  SHORT  HISTORY  OF  CHEMISTRY 

came  plain  through  the  researches  just  mentioned  and  especi- 
ally by  the  work  of  Liebig,  who  embodied  his  results  in  a 
pamphlet  published  about  1842.  With  reference  to  animal 
nutrition,  he  stated  that  it  was  based  upon  a  series  of  chemical 
reactions  and  distinguished  between  real  nutrients  and  sub- 
stances which  effect  animal  change  but  do  not  build  up  the 
tissues;  he  disproved  the  theory  (which  at  that  time  had 
held  sway  for  about  a  century)  that  plants  are  nourished  by  a 
certain  "humus"  in  the  soil,  and  showed  that  in  reality  they 
live  on  water,  carbonic  acid,  ammonia,  nitric  acid,  silica,  and  in 
lesser  degree  elements  such  as  phosphorus,  sulphur,  magnesium, 
calcium,  iron,  potassium,  which  are  built  up  into  complex  com- 
pounds in  the  vegetable  cells. 

This  work  is  of  course  the  foundation  of  scientific  agriculture, 
which  consists  in  supplying  to  a  crop  the  correct  amount  of  the 
constituents  needful  for  its  particular  development.  Very  much 
work  has  been  done  since  Liebig's  time  on  the  composition  of 
soils,  and  agricultural  chemistry  is  to-day  a  science  in  itself, 
special  laboratories  being  scattered  over  Europe  and  some  of 
the  British  colonies  for  the  investigation  of  plant-chemistry  and 
the  guidance  of  the  farmer. 

At  the  same,  time  the  selection  of  human  food  has  been  based 
upon  more  scientific  ground  owing  to  the  work  of  Liebig 
Pettenkofer,  Voit,  and  many  others,  while  the  importance  of 
controlling  its  quality  is  now  generally  recognized,  as  evidenced 
by  the  numerous  official  analysts  engaged  in  the  work  and  the 
recent  creation  (1908)  of  an  annual  international  congress  to 
advise  upon  legislation  respecting  matters  of  food  and  hygiene. 

Moreover,  the  rapid  extension  of  structural  knowledge  in 
organic  chemistry  has  encouraged  the  isolation  of  many  of  the 
complicated  substances  occurring  in  living  things  with  a  view  to 
elucidating  their  constitution.  Thus  chlorophyll,  the  colouring 
matter  of  leaves,  has  been  repeatedly  studied  (Sachs,  Pringsheim, 
etc.),  and  has  quite  recently  been  obtained  in  a  crystalline  state 
by  Willstatter.  Similarly  blood  (with  its  components  haemo- 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      139 

globin,  hsematin,  etc.)  has  frequently  received  attention  (Magnus, 
Meyer,  etc.  etc.),  and  so  have  other  organs  and  products  of  the 
animal  metabolism  such  as  flesh  (Liebig,  Strecker,  Helmholtz, 
Briicke),  fats  and  milk  (Chevreul),  saliva  (Leuchs  discovered  the 
enzyme ptyalin^  1831 ;  Ludwig,  Briicke),  gastric  juice  (Kiihne), 
and  urine  (Liebig  and  Voit  estimated  urea ;  Wohler  and 
Dessaignes  showed  formation  of  hippuric  acid ;  etc.),  the  names 
simply  indicating  one  or  two  of  the  foremost  workers. 

Side  by  side  with  the  efforts  to  ascertain  the  structure  of 
vegetable  and  animal  products  such  as  the  alkaloids,  or  sugars, 
numerous  attempts  have  been  made  to  produce  them  by  synthesis, 
and  in  not  a  few  cases  these  have  been  attended  with  success. 
Nevertheless  it  has  often  been  remarked  that  such  syntheses 
resemble  the  natural  process  in  little  more  than  the  identity  of 
the  end-product,  for  plants  and  animals  only  have  recourse  to 
agents  such  as  phosphorus  pentoxide  or  pentachloride,  potassium 
cyanide,  caustic  soda,  or  strong  sulphuric  acid  (to  name  a  few  of 
the  favourite  synthetic  laboratory  reagents)  under  the  most 
abnormal  and  dismal  conditions. 

We  cannot  unfortunately  trace  the  interesting  story  of  bio- 
logical chemistry  in  further  detail,  but  must  confine  ourselves 
to  a  description  of  the  chemical  development  of  four  important 
classes  of  naturally  occurring  organic  products,  viz.  the  alkaloids, 
the  terpenes,  the  sugars  and  other  "carbohydrates,"  and  the 
purines,  proteins  and  allied  nitrogenous  substances. 

§  2.  The  Alkaloids — The  presence  of  crystalline  basic  sub- 
stances in  certain  plant-juices  was  not  recognized  until  rather 
more  than  a  century  ago,  when  Seguin  prepared  "  morphium  " 
from  opium  (1803).  "Morphium"  was  soon  found  to  be  a 
mixture  of  several  bases,  from  which  one,  morphine,  was  isolated 
in  the  pure  state  by  Sertuerner  in  1817.  Other  allied  bodies 
such  as  strychnine,  quinine,  coniine  were  rapidly  discovered  and 
the  generic  name  of  alkaloids  was  given  to  them  on  account  of 
their  basic  properties.  Later  on,  Liebig  showed  that  the  latter 
was  due  to  the  nitrogen  present  in  all  the  compounds  concerned, 


140         A  SHORT  HISTORY  OF  CHEMISTRY 

and  much  more  recently,  when  the  constitutions  of  the  funda- 
mental types  of  organic  compounds  had  been  worked  out,  it  was 
found  that  most  alkaloids  could  be  broken  down  by  more  or  less 
violent  means  into  simpler  bodies,  allied  to  pyridine  (Konigs, 
Ladenburg,  Weidel).  In  consequence  of  this  and  of  the  pre- 
paration of  artificial  complex  pyridine  bases,  the  term  alkaloid 
is  now  generally  considered  to  embrace  all  basic  complex 
derivatives  of  pyridine  or  other  heterocyclic  nitrogenous  ring- 
system. 

Most  of  the  alkaloids  have  marked  therapeutic  (toxic  or 
anaesthetic)  properties  and  considerable  attention  has  therefore 
been  paid  to  their  detection  by  a  variety  of  reagents,  such  as 
double  metal  halides  (Pettenkofer,  1844),  phosphomolybdic  acid 
(Sonnenschein,  1856),  polyiodides  (Jorgensen,  1870),  or  hydro- 
ferrocyanic  acid  (E.  Fischer,  1877). 

So  various  have  been  the  methods  for  determining  alkaloid 
structure  and  attempting  alkaloid  synthesis  that  it  is  impossible 
to  name  them  here ;  we  can  only  give  a  summary  (p.  141)  of  the 
chief  men  connected  with  the  more  important  alkaloids  (with 
the  approximate  date  of  their  work)  and  mention  that  the  most 
prominent  workers  in  this  have  been  Pelletier  and  Caventou 
(1829),  Liebig  (1835),  Regnault  (1840),  Laurent  (1845),  Ander- 
son (1850),  Ladenburg  (1870-),  Skraup  (1880),  Freund,  Pschorr, 
Knorr,  Willstatter  (1890-),  A.  Pictet  (1895-). 

§  3.  The  Terpenes — The  chemical  history  of  the  "  essential 
oils  "  formed  by  many  plants  and  trees  falls  naturally  into  three 
divisions  : — 

(i)  A  preliminary  period,  in  which  crude  essences  were  ex- 
tracted from  the  plants,  chiefly  for  their  perfume  ;  this  extends 
to  the  remotest  times,  for  the  ancients  knew  how  to  make 
terpentine  oil  as  well  as  oils  of  olive,  almond,  pear,  etc.  (most 
of  which  have  been  already  dealt  with).  The  alchemists  added 
numerous  others,  such  as  those  from  rosemary,  thyme,  etc., 
and  the  group  of  herbal  essences  has  continued  to  multiply 
steadily. 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      141 


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142         A  SHORT  HISTORY  OF  CHEMISTRY 

(2)  An  intermediate  period,  extending  from  about  1810  to 
1870,  in  the  course  of  which  many  of  the  above  oils  were 
worked  up  and  pure  constituents  obtained ;  yet,  since  struc- 
tural   chemistry   was    not    at   the   time   sufficiently  advanced 
to  be  capable  of  explaining  their  constitution,   the  numerous 
investigators   had   in   most   instances  to  be  perforce  content 
with  denning  the  molecular  composition  and  the  characteristic 
reactions  of  their  various  products. 

(3)  The  period  in  which  the  constitution  of  terpenes  has 
been  seriously  investigated ;  this  did  not  commence  till  about 
1890,  but  since  that  date  an  enormous  mass  of  data  has  been 
and  is  being  accumulated  on  the  subject.     Tilden  (1880)  showed 
that  the  addition-products  of  the  terpenes  with  nitrosyl  chloride 
or  nitrous  anhydride  could  often  assist  in  determining  their 
structure,  and  from  1890  onwards  the  work  of  Baeyer,  Wallach, 
Wagner,  Kannonikow,  Kondakow,  Bredt,  Briihl,  Barbier,  Harries, 
Tiemann,  Semmler,  and  their  students,  has  been  especially  im- 
portant in  elucidating  this  very  complicated  problem.     In  1894 
a  convenient  nomenclature  for  the  class  of  terpenes  was  arrived 
at,    mainly  by  Baeyer   and  Wagner ;  the  only  other   general 
statement  it  is  possible  to  make   here  refers  to  the  syntheses 
of  members  of  the  series,  carried  out  by  Baeyer  in  1893  (from 
succino-succinic  ester  derivatives)  and  by  W.  H.  Perkin,  jun., 
since  1 905  (mainly  by  the  help  of  the  Grignard  reagent).     Of 
these  it  is  only  the  latter  which  has  yielded  terpenes  identical 
with  previously  known  natural  products.     The  table  on  p.  143 
summarizes  the  history  of  a  few  typical  terpenes. 

§  4.  Sugars  and  other  Carbohydrates ;  Glucosides— 
The  sugars  form  yet  another  class  of  compounds  which  have 
served  to  prove  the  capabilities  of  the  modern  structural  theory 
of  organic  compounds  for  although  numerous  sugars  were 
known  before  the  latter  took  firm  hold,  their  constitutions  re 
mained  unfathomed  until  about  1885.  Since  then  the  whole 
maze  of  stereo-isomeric  sugars  has  been  cleared  up  and  system- 
atized, notably  owing  to  the  great  work  of  Emil  Fischer ;  and  as 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      143 


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144         A  SHORT  HISTORY  OK  CHEMISTRY 

a  secondary  result  various  artificial  sugars  have  been  produced 
in  accordance  with  the  indications  of  the  theoretical  formulae. 

We  must  first  glance  at  some  of  the  means  which  have  served 
to  characterize  the  otherwise  not  very  well-defined  members  of 
the  class.  Their  optical  rotatory  power  (frequently  showing 
mutarotation)  has  long  been  used  as  a  test,  and  so  has  the  re- 
ducing power  which  most  of  them  exert  on  ammoniacal  copper 
solutions  (Fehling,  1849).  Of  their  crystalline  derivatives  the 
phenylhydrazones  and  osazones  (E.  Fischer,  1884)  are  especially 
useful  on  account  of  their  superior  power  of  crystallization. 

The  most  interesting  part  of  their  history,  however,  deals  with 
the  complicated  syntheses  which  in  a  few  master  hands  have  led 
up  to  our  present  extensive  knowledge  of  their  configuration. 

It  was  not  until   1880  that  the  general  nature  of  a  sugar 
(aldehyde-alcohol)  was  realized  (by  Zincke),  although  in  1861 
Butlerow  had  produced  a  sugar-like  syrup,  "  methyleneitan,"  by 
alkaline  condensation  of  trioxymethylene    (polymerized   form- 
aldehyde).     Similar    syntheses  were  achieved   by  Loew,  who 
obtained  unfermentable  "  formose  "  by  condensation  of  form- 
aldehyde with  lime  (1886),  and  fermentable  "  methose  "  when 
magnesia  replaced  the  lime  (1889).     E.  Fischer's  work  com- 
menced about    1884  with  the  investigation  of  the  action  of 
phenylhydrazine  on  sugars,  and  in  1887  he  obtained  "a-acrose" 
(afterwards  shown  to  be  <//- fructose)  by  the  action  of  baryta  on 
dibrom-acrolein.     In  the  meantime  Kiliani  developed  methods 
for  increasing  the  number  of  carbon  atoms  in  a  sugar  by  utiliz- 
ing the  hydrogen  cyanide  addition-products  (1885-6),  and  Fischer 
showed  in  1 8 90  how  the  resulting  oxy-acids  (from  the  cyanhydrin 
hydrolysis)  might  be  reduced  to  new  sugars  by  sodium  amalgam. 
By  these  means  he  completed  the  synthesis  of  d-  and  /-  glucose, 
and  d-  and  /-fructose  and  numerous  other  sugars,  and  by  about 
1894  had  worked  out  with  tolerable  certainty  the  spacial  con- 
figurations of  the  sixteen  possible  aldohexoses,  the  keto-hexoses, 
the  eight  possible  aldopentoses,  etc.,  and  had  deduced  there- 
from  the  configuration  of  d-  and  /-tartaric   acids.      Further 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      145 

methods  which  tended  to  confirm  all  these  theories  were  sup- 
plied by  the  reactions  of  Wohl  (1893)  and  Ruff  (1898),  which 
permit  of  the  degradation  of  a  sugar  to  one  containing  one  atom 
of  carbon  less  in  the  molecule. 

At  the  same  time  the  constitution  of  the  di-  and  tri-sac- 
charides,  such  as  cane-sugar  or  raffinose,  has  been  partially, 
cleared  up,  for  in  1893  Fischer  prepared  alkyl  ethers  of  the 
alcohols  which  were  chemically  analogous  to  the  natural  gluco- 
sides,  and  later  it  has  appeared  (Tanret,  1895  ;  Perkin,  1902  ; 
E.  F.  Armstrong,  1903)  that  the  poly-saccharides  are  consti- 
tuted similarly  to  the  synthetic  glucosides,  and  are,  therefore, 
condensation-products  or  "  mixed  ethers "  of  the  different 
mono-saccharides  (hexoses). 

The  structure  of  other  carbohydrates — those  of  the  formula 
(C6H10O5)n,  where  n  is  at  present  unknown,  but  certainly  very 
large — has  not  yet  been  arrived  at,  and  it  would  seem  that  it  will 
remain  an  unsolved  problem  for  some  time  to  come. 

We  proceed  to  the  usual  historical  summary  (p.  146)  of 
the  class  we  have  discussed,  adding  also  a  list  of  the  most 
interesting  natural  glucosides  (or  sugar  ethers).  The  existence 
of  certain  natural  hydro-aromatic  sugars,  such  as  inosite 
(Scherer,  1850)  or  quercite  (Hofmann,  1877),  should  not  be 
overlooked. 

§  5.  Amido  Acids,  Proteins,  and  Purines— The  alka- 
loids and  the  terpenes  are  exclusively  vegetable  substances,  the 
sugars  occur  chiefly  in  the  vegetable,  but  also  in  the  animal 
kingdom ;  the  last  group  which  remains  to  be  considered  is 
common  to  both,  but  plays  an  exceedingly  important  part  in 
animal  metabolism.  This  series,  comprising  organic  bodies 
containing  one  (and  usually  several)  groups  of  the  type 
— NH.CH2.CO — ,  has  been  persistently  investigated  for 
nearly  a  hundred  years,  but  at  present,  although  it  may  be  said 
that  a  general  knowledge  of  its  members  has  now  been  at- 
tained, there  remain  many  of  its  naturally-occurring  deriva- 
tives whose  constitution  has  not  been  unravelled,  and  still 
10 


146        A  SHORT  HISTORY  OF  CHEMISTRY 


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CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      147 

more  whose  supposed  structure  has  not  been  confirmed  by 
synthesis. 

The  first  indications  of  the  important  natural  role  of  sub- 
stances containing  this  group  came  as  early  as  1820,  when 
Braconnot  obtained  a  substance  "  glycocoll  "  by  boiling  glue 
with  dilute  acids.  In  the  ensuing  thirty  or  forty  years  various 
other  compounds,  which  bore  more  or  less  chemical  resem- 
blance to  glycocoll,  were  prepared  from  meat  extract,  milk, 
bile  and  similar  animal  juices.  Liebig,  Wohler,  Liebreich  and 
others  subsequently  found  that  the  cause  of  the  similarity  lay 
in  the  fact  that  the  creatine,  tyrosine,  asparagine,  serine  (to 
name  only  a  few  of  the  compounds  in  question)  were  all  deriv- 
atives of  the  amido-acids.  This  naturally  led  to  synthetical 
work  on  the  amido-acids,  commenced  by  Strecker  about  1860, 
and  continued  by  numerous  chemists  down  to  Erlenmeyer, 
Curtius,  and  especially  Emil  Fischer,  the  present-day  workers 
in  this  branch. 

In  this  way  it  was  soon  found  (cf.  the  table  which  follows) 
that  a  number  of  these  animal  decomposition-products  were 
either  amido-acids  (e.g.  glycocoll,  tyrosine),  cyclic  anhydrides 
of  amido-acids  (creatine,  betaine),  amides  of  amido-acids  (as- 
paragine, urea,  guanidine),  or  more  complicated  amido-acid 
derivatives,  such  as  cystine,  tryptophane,  or  proline  (some  of 
the  most  recently  added  members).  Moreover,  the  ptomaines 
or  "  corpse  alkaloids,"  poisonous  products  of  animal  decay,  were 
also  found  to  be  closely  related  to  the  above  (Selmi,  1872), 
being  simple  aliphatic  diamines. 

More  important  than  all  this,  however,  are  the  efforts  which 
have  been  made  with  no  small  success  to  trace  a  connexion 
between  such  chemically  simple  end  products  of  decomposition 
and  the  complicated  components  of  living  bodies  known  as  albu- 
mens. Various  workers  have  shown  within  the  last  twenty  years 
that  the  molecular  magnitude  of  such  substances  (e.g.  casein, 
haemoglobin,  etc.)  is  very  large,  and  cannot  fall  short  of  16,000 
in  most  cases ;  but.no  precise  conception  of  albuminoid  struc- 


148          A  SHORT  HISTORY  OF  CHEMISTRY 

ture  was  arrived  at  until  Fischer  turned  his  attention  to  the 
problem  about  1900,  having  solved  those  of  the  sugars  and  of 
the  purines  (to  which  we  shall  shortly  refer).  His  work  is 
too  extensive  to  recount  in  detail,  but  it  may  be  summed 
up  in  the  diagram  which  he  has  succeeded  in  drawing  up 
to  show  the  successive  decompositions  of  an  albuminous  sub- 
stance : — 

ALBUMEN  (nucleo-protein) 
(pepsin  |  hydrolysis). 


ALBUMOSE  (nuclein)  PROTEIN  decomposition-products, 

(trypsin  |  hydrolysis). 


PEPTONE  (nucleic  acid)  PROTEIN  decomposition-products, 

(acid  |  hydrolysis). 

I 
Amido-acids,  phosphoric  acid,  purine  bases,  sugars. 

From  these  protein  or  polypeptide  decomposition-products 
Fischer  has  isolated  definite  compounds  of  the  general  structure 
NH2[CH2.CO.NH]n.CH2.COOH,  and,  on  the  other  hand, 
he  has  synthesized  chemically  similar  substances  (although  of 
less  molecular  weight)  from  simple  amido-acids  by  a  variety 
of  methods,  obtaining  in  the  latest  instance  an  octadeca- 
peptide  containing  fifteen  glycocoll  and  three  leucine  groups 
(1907). 

He  has  thus  shown  the  general  nature  of  the  proteins  and, 
consequently,  of  the  albumens. 

For  a  number  of  years  previous  to  the  protein  work  he  was 
engaged  in  consummating  by  decomposition,  as  well  as  by 
synthesis,  the  knowledge  of  another  group  of  natural  products 
such  as  caffeine,  uric  acid,  xanthine,  guanine  (previously  studied 
by  Liebig,  Strecker,  Baeyer,  and  many  others),  all  of  which  he 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIFE      149 
proved   to   be   derivatives   of  a   parent  substance   "  purine," 


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which  he  finally  prepared  (1898).  This  remarkable  work 
(sugars — purines — proteins)  is  one  of  the  most  complete  series 
of  investigations  on  record  in  chemical  history. 

Since  1900  W.  Traube  has  also  contributed  a  number  of 
independent  syntheses  of  most  of  the  purines. 

In  the  following  table  the  various  natural  amido-acid  or 
amido-acyl  products  are  grouped  according  to  the  order  in 
which  they  have  been  discussed  above : — 


150         A  SHORT  HISTORY  OF  CHEMISTRY 


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152          A  SHORT  HISTORY  OF  CHEMISTRY 

§  6.  Fermentation  and  Enzyme-Action — We  will  con- 
clude this  chapter  with  a  reference  to  the  part  played  by  certain 
bacteria  and  imitated  by  a  number  of  lifeless  substances  in  pro- 
moting many  chemical  actions,  and  usually  denoted  by  the 
phrase  fermentation.  The  formation  of  wines  from  grape-juice 
was  ascribed  to  this  process  centuries  ago,  and  van  Helmont 
went  so  far  as  to  say  that  "  fermentation  "  was  the  principal 
cause  of  all  organic  processes,  but  it  is  doubtful  whether  he 
used  the  terms  with  anything  approaching  their  modern  signi- 
fication. At  all  events  the  real  nature  of  vinous  fermentation 
was  not  appreciated  in  his  day,  for  it  was  not  until  1680  that 
Becher  showed  that  sugar  must  be  present,  while  the  fact  that 
the  alcohol  and  carbonic  acid  come  directly  from  this  sugar 
was  only  revealed  by  Lavoisier  in  1783.  During  the  next 
half-century,  however,  numerous  other  cases  of  ferment  action 
came  to  light  (lactic  acid,  higher  alcohols,  etc.),  and  it  was  also 
realized  that  many  of  the  chemical  reactions  going  orf  in  animal 
bodies  are  maintained  by  the  agency  of  ferments. 

Theories  were  not  wanting  to  "  explain  "  the  mechanism  of 
the  process;  we  may  refer  to  the  Berzelius-Mitscherlich  "con- 
tact "  theory  (1834-6)  and  to  Liebig's  "  vibration  "  theory  (1839) 
which  assumed  that  ferments  were  in  a  state  of  continual  mole- 
cular oscillation  which  induced  a  similar  vibration  (causing 
molecular  disruption)  in  certain  other  molecules.  Such  hypo- 
theses had  little  if  any  experimental  support,  and  indeed  a 
discovery  made  by  Cagniard  de  la  Tour  three  years  prior  to 
Liebig's  hypothesis  pointed  to  a  very  different  explanation,  for  it 
was  found  that  the  yeast  cells  present  during  sugar  fermentation 
actually  multiplied  in  the  process.  Later  on  it  was  observed 
that  not  all  the  known  ferments  grew  in  this  manner,  but  only 
definite  members  of  the  class,  but  little  of  importance  was 
settled  with  regard  to  the  subject  until  in  1855  Pasteur  collated 
all  the  known  facts,  and  after  much  investigation  elaborated 
his  "  vitalistic "  theory,  declaring  that  all  real  fermentations 
were  the  results  of  the  action  and  multiplication  of  living  or- 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LIF£      i$$ 

ganisms.  This,  while  giving  a  partial  insight  into  ferment 
action,  did  not  explain  the  processes  involved  in  the  case  of 
those  ferments  such  as  emulsin  (1830,  Robiquet),  ptyalin 
(1831,  Leuchs),  diastase  (1834,  Payen  and  Persoz),  pepsin 
(1835,  Schwann),  invertase  (1870,  Liebig)  and  "  inorganic  fer- 
ments" (colloidal  platinum,  etc.)  which  are  not  made  up  of 
living  cells  at  all ;  all  these  were  set  by  Pasteur  in  a  separate 
class — the  enzymes  or  unorganized  ferments. 

Much  work  has  since  been  undertaken  on  this  very  difficult 
problem,  but  although  Pasteur's  generalizations  have  held  their 
place,  it  must  be  admitted  that  there  is  much  that  is  arbitrary 
and  unsatisfying  in  his  explanation.  Again,  Buchner  has 
shown  (1896)  that  sugar  is  fermentable  by  a  juice  present  in 
yeast,  but  not  containing  any  living  cells,  and  so  it  would 
seem  that  possibly  the  vitalistic  theory  may  yet  give  way  to  a 
more  general  solution  embracing  both  organized  ferments  and 
enzymes. 

Other  recent  students  include  Knap,  Nef,  Meissheimer  and 
Emmerling ;  the  latter  showed  in  1901  that  in  some  cases 
enzyme  action  is  reversible,  i.e.  the  same  product  which  de- 
composes a  glucoside,  for  example,  may  under  given  conditions 
bring  about  its  synthesis  from  its  hydrolysis  products. 

The  mechanism  of  fermentation  was  first  studied  from  a 
physico-chemical  standpoint  by  Wilhelmy  in  1850;  later 
workers  include  O'Sullivan  (1885-1900),  Adrian  and  Horace 
Brown  (1892-),  and  E.  F.  Armstrong  (1904)1  The  general 
result  has  been  that,  although  at  one  time  apparent  exceptions 
were  encountered,  fermentation  proceeds  strictly  according  to 
the  law  of  mass-action,  and  conforms  just  like  any  other  chemi- 
cal change  to  the  laws  of  chemical  kinetics. 


152          A  SHORT  HISTORY  OF  CHEMISTRY 

§  6.  Fermentation  and  Enzyme- Action — We  will  con- 
clude this  chapter  with  a  reference  to  the  part  played  by  certain 
bacteria  and  imitated  by  a  number  of  lifeless  substances  in  pro- 
moting many  chemical  actions,  and  usually  denoted  by  the 
phrase  fermentation.  The  formation  of  wines  from  grape-juice 
was  ascribed  to  this  process  centuries  ago,  and  van  Helmont 
went  so  far  as  to  say  that  "  fermentation  "  was  the  principal 
cause  of  all  organic  processes,  but  it  is  doubtful  whether  he 
used  the  terms  with  anything  approaching  their  modern  signi- 
fication. At  all  events  the  real  nature  of  vinous  fermentation 
was  not  appreciated  in  his  day,  for  it  was  not  until  1680  that 
Becher  showed  that  sugar  must  be  present,  while  the  fact  that 
the  alcohol  and  carbonic  acid  come  directly  from  this  sugar 
was  only  revealed  by  Lavoisier  in  1783.  During  the  next 
half-century,  however,  numerous  other  cases  of  ferment  action 
came  to  light  (lactic  acid,  higher  alcohols,  etc.),  and  it  was  also 
realized  that  many  of  the  chemical  reactions  going  orf  in  animal 
bodies  are  maintained  by  the  agency  of  ferments. 

Theories  were  not  wanting  to  "  explain  "  the  mechanism  of 
the  process;  we  may  refer  to  the  Berzelius-Mitscherlich  "con- 
tact M  theory  (1834-6)  and  to  Liebig's  "  vibration  "  theory  (1839) 
which  assumed  that  ferments  were  in  a  state  of  continual  mole- 
cular oscillation  which  induced  a  similar  vibration  (causing 
molecular  disruption)  in  certain  other  molecules.  Such  hypo- 
theses had  little  if  any  experimental  support,  and  indeed  a 
discovery  made  by  Cagniard  de  la  Tour  three  years  prior  to 
Liebig's  hypothesis  pointed  to  a  very  different  explanation,  for  it 
was  found  that  the  yeast  cells  present  during  sugar  fermentation 
actually  multiplied  in  the  process.  Later  on  it  was  observed 
that  not  all  the  known  ferments  grew  in  this  manner,  but  only 
definite  members  of  the  class,  but  little  of  importance  was 
settled  with  regard  to  the  subject  until  in  1855  Pasteur  collated 
all  the  known  facts,  and  after  much  investigation  elaborated 
his  "  vitalistic "  theory,  declaring  that  all  real  fermentations 
were  the  results  of  the  action  and  multiplication  of  living  or- 


CHEMISTRY  OF  PLANT  AND  ANIMAL  LlF£      i$$ 

ganisms.  This,  while  giving  a  partial  insight  into  ferment 
action,  did  not  explain  the  processes  involved  in  the  case  of 
those  ferments  such  as  emulsin  (1830,  Robiquet),  ptyalin 
(1831,  Leuchs),  diastase  (1834,  Payen  and  Persoz),  pepsin 
(1835,  Schwann),  invertase  (1870,  Liebig)  and  "  inorganic  fer- 
ments" (colloidal  platinum,  etc.)  which  are  not  made  up  of 
living  cells  at  all ;  all  these  were  set  by  Pasteur  in  a  separate 
class — the  enzymes  or  unorganized  ferments. 

Much  work  has  since  been  undertaken  on  this  very  difficult 
problem,  but  although  Pasteur's  generalizations  have  held  their 
place,  it  must  be  admitted  that  there  is  much  that  is  arbitrary 
and  unsatisfying  in  his  explanation.  Again,  Buchner  has 
shown  (1896)  that  sugar  is  fermentable  by  a  juice  present  in 
yeast,  but  not  containing  any  living  cells,  and  so  it  would 
seem  that  possibly  the  vitalistic  theory  may  yet  give  way  to  a 
more  general  solution  embracing  both  organized  ferments  and 
enzymes. 

Other  recent  students  include  Knap,  Nef,  Meissheimer  and 
Emmerling;  the  latter  showed  in  1901  that  in  some  cases 
enzyme  action  is  reversible,  i.e.  the  same  product  which  de- 
composes a  glucoside,  for  example,  may  under  given  conditions 
bring  about  its  synthesis  from  its  hydrolysis  products. 

The  mechanism  of  fermentation  was  first  studied  from  a 
physico-chemical  standpoint  by  Wilhelmy  in  1850;  later 
workers  include  O'Sullivan  (1885-1900),  Adrian  and  Horace 
Brown  (1892-),  and  E.  F.  Armstrong  (1904).  The  general 
result  has  been  that,  although  at  one  time  apparent  exceptions 
were  encountered,  fermentation  proceeds  strictly  according  to 
the  law  of  mass-action,  and  conforms  just  like  any  other  chemi- 
cal change  to  the  laws  of  chemical  kinetics. 


CHAPTER  IX 

THE  APPLICATION  OF  CHEMISTRY  TO 
MANUFACTURES 

To  omit  any  reference  to  the  part  chemistry  has  played  in  en- 
gineering, agriculture,  dyeing  and  many  other  equally  con- 
spicuous aids  to  what  is  called  civilized  existence  would  be  to 
render  a  very  one-sided  record  of  chemical  history.  On  the 
other  hand,  it  is  obviously  impossible  to  chronicle  all  the  tech- 
nical improvements  made  in  manufacturing  processes,  more 
particularly  within  the  last  hundred  years.  We  will  therefore 
refer  briefly  to  the  more  notable  applications  of  pure  chemistry 
to  "  the  arts,"  ranging  from  the  earliest  (the  purification  of  gold, 
silver  and  other  metals  easily  obtained  from  their  ores)  to  the 
most  recent  products  of  civilization  (the  use  of  electricity  and 
petrol ;  the  invention  of  "  high  "  explosives). 

The  parts  of  the  globe  noted  for  excellence  of  technical 
work  have  extended  at  different  periods  from  eastern  to  western 
hemispheres.  The  ancient  oriental  peoples  are  the  earliest 
that  we  can  say  with  certainty  applied  chemistry  (albeit  in  >an 
empirical  manner)  to  manufactures  (e.g.  Chinese  pottery  and 
Egyptian  colouring).  During  the  Middle  Ages,  Italy  and  France 
were  the  most  prominent  countries  in  this  respect,  and  later 
came  the  modern  supremacy  of  England.  Most  recently  there 
has  been  witnessed  a  remarkable  development  of  industrial 
operations  in  Germany,  which  has  given  rise  to  much  pessimistic 
talk  in  England.  But  if  British  manufacturers  show  more 
readiness  to  adopt  the  latest  technical  devices,  and  give  adequate 
support  to  the  facilities  now  available  for  the  instruction  of  their 


THE  APPLICATION  OF  CHEMISTRY         155 

workers,  little  fear  need  be  entertained  as  to  whether  our  coun- 
try can  "  hold  its  place  ".  Finally,  the  modern  system  of  transit, 
etc.,  has  modified  the  location  of  factories,  so  that  whilst  in  some 
cases  raw  material  is  brought  to  the  centres  of  civilization  for 
fabrication,  in  many  others  the  ore,  crop,  or  whatever  it  may 
be,  is  worked  up  in  distant  parts  of  the  world  close  to  its 
natural  source. 

Turning  to  the  purely  scientific  side  of  the  subject,  it  will  be 
well  to  point  out  how,  especially  of  recent  years,  purely  theo- 
retical researches  have  assisted  the  manufacturer.  We  may  do 
this  best  by  giving  a  few  concrete  examples  : — 

(1)  Le  Chatelier's  work  on  the  "  phases "  and  the  thermal 
conditions  prevailing  in  the  blast  furnace. 

(2)  The  same   physical  chemist's  research  on  the  conditions 
of  equilibrium  of  the  reactions  CaCO3^±CaO  +  CO2  and  CO2 
^CO  +  O. 

(3)  The  elaborate  electrochemical  and  thermochemical  theories 
upon  which  the  processes   for  the   "  fixation  of  atmospheric 
nitrogen  "  (§  3)  are  based. 

(4)  The  difficulties  (only  overcome  by  years  of  research)  in 
the  practical  application  of  the  sulphuric  acid  "  contact  process  ". 

(5)  Syntheses  of  various  organic  compounds  have  provided 
means   for   supplying  many  products  more  cheaply  (alizarin, 
indigo,  etc.). 

We  will  now  proceed  to  give  a  more  detailed  account  of  this 
practical  application  of  results  obtained  in  the  laboratory. 

§  i .  The  Preparation  of  Useful  Elements.  Metallurgy 
— Taking  first  the  larger  branch — metallurgy — of  this  division, 
we  may  divide  modern  practical  methods  as  follows : — 

(a)  Those  which  are  simply  improvements  of  older  fundamental 
principles. 

(p)  Those  which  involve  entirely  new  processes  (in  most  in- 
stances the  application  of  electricity], 

(a)  The  principle  of  the  smelting  of  a  few  ores,  such  as  those 
of  lead,  tin,  copper,  and  mercury,  remains  the  same  to-day  as 


156         A  SHORT  HISTORY  OF  CHEMISTRY 

when  directions  for  making  these  metals  were  recorded  by  Greek 
and  Roman  philosophers.  These  directions  were  naturally 
simply  of  the  nature  of  recipes,  the  explanation  of  the  different 
processes  being  but  imperfectly  understood  all  through  the  al- 
chemical and  phlogistic  periods.  The  alchemists,  however,  knew 
sufficient  to  enable  them  to  use  a  rough  sort  of  analysis  as  a 
check  on  the  purity  of  their  products,  the  first  advice  on  the 
subject  of  assaying  appearing  in  the  works  of  Agricola  and 
Libavius. 

Modern  modifications  have  consisted  here  in  the  use  of  a 
"  wet  process  "  (Hunt  and  Douglas)  and  an  electrolytic  pre- 
cipitation process  (Elsmore,  Siemens,  and  others)  for  copper, 
methods  of  desilverizing  lead  (Pattinson,  Parkes),  and  economic 
improvements  in  the  metallurgy  of  some  other  elements,  such  as 
zinc  (Marggraf,  Stromeyer). 

Among  elements  which  are  still  obtained  by  processes  cen- 
turies old  we  may  mention  mercury,  sulphur,  bismuth,  and  tin- 

The  metals  of  the  platinum  group  were  first  isolated  on  a 
commercial  scale  by  Cock  (1800-1808)  in  the  form  of  impure 
platinum ;  Deville  and  Debray  constructed  a  furnace  for  the 
fusion  of  these  metals  and  Matthey  showed  how  to  separate  and 
purify  them. 

Before  dealing  with  the  iron  industry  (the  most  important  of 
this  section),  we  will  recall  the  introduction  of  electro-plating 
by  De  la  Rive  in  1836  and  Jacobi  in  1839,  a  method  which  was 
extended  during  the  next  generation  to  the  cases  of  copper, 
silver,  gold,  nickel,  and  manganese,  amongst  others. 

The  manufacture  of  iron  and  steel  went  on  by  the  old  Catalan 
and  allied  processes  until  in  1784  Cort  introduced  the  puddling 
process  for  wrought  iron ;  another  important  improvement  was 
the  substitution  of  hot  for  cold  air  in  the  blast  for  the  furnaces 
(Neilson,  1828).  Between  1856  and  1867  the  Bessemer  process 
for  converting  cast  iron  to  steel  was  perfected ;  contempor- 
aneously another  method  was  introduced  by  Siemens  and 
Martin.  These  were  improved  upon  by  the  Thomas-Gilchrist 


THE  APPLICATION  OF  CHEMISTRY          157 

process  (1878-80) ;  Wagner  has  shown  how  the  slag  from  this 
process,  rich  in  phosphates,  may  be  utilized  agriculturally  as  a 
manure.  Such  is  a  bare  outline  of  one  of  the  most  important 
British  industries ;  other  points  of  scientific  interest  include  the 
researches  of  Bunsen  and  Playfair  on  the  composition  of 
furnace-gases,  and  the  utilization  of  the  spectroscope  by  Bradge 
and  Roscoe  to  detect  the  end  point  of  the  reaction  in  the  Bes- 
semer process. 

(b)  The  newer  methods  of  element  manufacture  apply  as  a 
rule  to  elements  difficult  to  isolate  from  their  compounds  and 
consist  mainly  of  electrolytic  processes  and  processes  involving 
extremely  high  temperatures. 

The  first  type  includes  the  modern  manufacture  of  the  alkali 
and  alkaline  earth  metals,  magnesium,  aluminium,  etc.  Of 
these,  the  alkalies  were  formerly  made  by  violent  reduction 
processes;  calcium,  strontium,and  barium  had  only  been  obtained 
impure  by  the  action  of  sodium  amalgam  on  their  salts,  and  the 
rest  were  made  by  fusing  their  chlorides  with  sodium  (Wohler, 
Deville).  The  case  of  the  alkali  elements  is  particularly  in- 
teresting ;  Davy's  electrolytic  isolation  of  these  was  regarded  as 
of  purely  theoretical  interest,  and  Gay-Lussac  and  The"nard 
tried  to  manufacture  sodium  commercially  by  heating  iron  with 
fused  caustic  soda.  Later,  in  1823,  Brunner  showed  how 
potassium  resulted  from  the  ignition  of  an  intimate  mixture  of 
the  carbonate  and  charcoal;  Deville  improved  upon  this  by 
igniting  a  paste  made  of  soda  and  chalk  with  oil.  ,  Such  methods 
were  comparatively  costly,  but  the  electrolysis  of  the  fused 
chloride  or  hydrate  on  a  commercial  scale  by  Castner  (1890) 
furnished  a  cheap  means  of  preparing  the  pure  elements.  A 
further  modification  is  the  electrolysis  of  the  aqueous  alkalies 
with  a  mercury  cathode,  with  which  the  liberated  element  at 
once  amalgamates.  The  alkaline  earth  and  other  elements  are 
all  prepared  at  the  present  day  by  electrolysis  of  their  fused 
chlorides  (in  the  case  of  aluminium,  electrolysis  of  a  solution  of 
bauxite  AIO(OH)  in  fused  cryolite  A1F3,  3NaF). 


158         A  SHORT  HISTORY  OF  CHEMISTRY 

Reduction  of  refractory  oxides  at  high  temperatures  has  been 
carried  out  of  recent  years  by  Moissan  (a  mixture  of  charcoal 
and  oxide  of  uranium,  tungsten,  manganese,  chromium,  silicon, 
or  titanium  being  heated  in  the  electric  furnace,  1893-6),  by 
Readman  and  Parker  (phosphorus  from  phosphates,  sand,  and 
coke  in  an  electric  furnace,  1902),  and  by  the  "thermite" 
process  of  Goldschmidt  (1898),  an  intimate  mixture  of  aluminium 
powder  and  an  oxide  of  iron,  nickel  chromium,  manganese,  etc., 
which  on  ignition  by  a  thermo-detonator  yields  the  metal  and 
alumina  with  evolution  of  much  heat. 

The  manner  in  which  of  late  years  manufactories  for  the  pro- 
duction of  the  rarer  elements  and  compounds  have  sprung  up 
is  noteworthy ;  we  may  instance  those  for  the  rare  earth  oxides 
and  elements  (for  Welsbach  "  mantles,"  etc.),  as  well  as  the  new 
factory  in  London  for  uranium  and  radium  compounds.  The 
use  of  potassium  cyanide  in  gold  and  silver  extraction  is  a 
metallurgical  improvement  which  has  now  been  applied  for 
many  years. 

The  technical  history  of  a  few  gaseous  elements  is  also  in- 
teresting ;  chlorine,  for  example,  was  manufactured  on  modern 
lines  by  Weldon  (1868)  from  pyrolusite,  an  important  addition 
being  the  Weldon- Pechiney  method  of  recovering  the  man- 
ganese (1882);  another  method  (decomposition  of  HC1  by 
heated  copper  salts)  was  devised  by  Deacon  (about  1880),  while 
at  the  present  time  a  large  amount  of  chlorine  is  produced  in 
the  Kellner-Castner  electrolytic  process  for  caustic  soda  from 
brine  (see  §  2). 

Finally,  nitrogen  and  oxygen  are  now  exclusively  prepared  by 
the  fractional  distillation  of  liquid  air,  the  older  methods  of 
depriving  air  of  oxygen  by  barium  oxide  (Brin,  1881)  and  re- 
covering the  oxygen  from  the  barium  peroxide  formed,  having 
failed  to  compete  successfully  with  the  newer  process. 

§  2.  The  Alkali,  Sulphuric  Acid,  Vinegar  and  similar 
Industries — We  have  next  to  deal  with  a  number  of  industries 
which  usually  go  by  the  name  of  "chemical  manufactures,"  and 


THE  APPLICATION  OF  CHEMISTRY          159 

we  may  take  the  "  soda  industry  "  as  one  of  the  most  important 
instances.  Sodium  and  potassium  carbonates  were  made  in 
olden  days  by  incinerating  sea-shore  plants  ("barilla"),  but 
towards  the  close  of  the  phlogistic  period  search  was  made  for  a 
better  method.  The  clue  to  this  improvement  was  supplied  by 
Guyton  de  Morveau  in  1782,  who  showed  that  soda  is  formed 
when  Glauber's  salt  is  heated  strongly  with  coal  and  iron. 
Leblanc  (1787-91)  based  his  process  upon  this  observation, 
preparing  the  sulphate  from  common  salt  and  then  heating  it  with 
coal  and  chalk,  finally  obtaining  the  carbonate  from  this  by 
washing  with  water.  The  system  was  first  worked  in  England 
by  Muspratt  in  1824. 

Some  fourteen  years  later  Dyar  and  Hemming  took  out  a 
patent  for  obtaining  soda  crystals  from  common  salt  by  the 
action  of  carbonic  acid  in  the  form  of  ammonium  carbonate. 
This  was  improved  by  Solvay  in  1861  and  adopted  in  1874  in 
England  at  Brunner,  Mond  &  Co.'s  works.  Finally,  Har- 
greaves  and  Bird  (1896)  have  introduced  an  electrolytic  method 
for  soda  production  from  salt,  using  a  special  electrode  per- 
meable to  sodium  ions,  but  not  to  brine,  and  supplying  a  stream 
of  carbon  dioxide  externally  to  the  electrodes  whereby  the 
product  obtained  is  soda  crystals  or  simply  caustic  soda  as 
required. 

These  two  last  methods  have  cheapened  soda-fabrication  to 
such  an  extent  that  the  Leblanc  process  is  now  only  valuable 
for  its  bye-products — hydrochloric  acid,  first  collected  as  an 
aqueous  solution  from  the  conversion  of  the  salt  to  sulphate  by 
Gossage  (1836),  and  sulphur  and  sulphides  of  calcium,  utilized 
by  the  recovery  processes  of  Chance  (1888)  and  others. 

Caustic  soda  itself  used  to  be  made  technically  (from  1850 
onwards)  by  "  causticising  "  soda  solutions  with  lime,  filtering 
from  chalk  and  concentrating.  About  1885  the  Castner-Kellner 
process  of  electrolysing  brine  with  a  movable  mercury  cathode 
came  into  operation  ;  the  mercury  is  first  made  to  act  as  cathode 
and  then  decomposed  by  water  by  mechanical  oscillation.  Later 


160         A  SHORT  HISTORY  OF  CHEMISTRY 

processes  have  all  been  modifications  of  the  electrolytic  prin- 
ciple. 

We  have  just  indicated  the  chief  source  of  hydrochloric  acid  ; 
of  the  other  two  most  important  mineral  acids  there  is  little 
of  note  in  the  preparation  of  nitric  acid  (for  which  Boyle  gave 
the  first  technical  directions)  except  the  recent  electrical  methods 
mentioned  in  the  next  paragraph.  The  means  of  producing  oil 
of  vitriol,  on  the  other  hand,  have  varied  a  good  deal.  First 
manufactured  by  the  Nordhausen  method  (distillation  of 
green  vitriol)  in  alchemical  times,  a  great  improvement  was 
effected  in  its  fabrication  by  Roebuck  (1746)  at  Birmingham, 
Gay-Lussac  (1824),  and  Glover  (1841),  who  evolved  between 
them  the  "  lead  chamber  process  ".  More  recently  this  has 
been  in  part  superseded  by  the  "  contact  process,"  in  which 
sulphur  dioxide  and  oxygen  unite  by  the  catalytic  action  of 
finely-divided  platinum.  A  patent  covering  this  method  appears 
under  the  name  of  Philips  as  far  back  as  1831,  but  it  was  not 
till  about  1875  tnat  a  practical  paying  process  was  devised 
(Winkler,  Knietsch).  Since  1900  the  Badische  Anilin  und  Soda 
Fabrik  have  improved  it  in  various  directions,  such  as  eliminat- 
ing traces  of  arsenic  (which  "  poisons  "  the  platinum)  from  the 
mixed  gases,  and  employing  sulphates  of  cerium,  lanthanum,  and 
other  rare  earth  metals  as  additional  catalysts. 

Of  other  inorganic  chemicals  produced  in  large  quantities 
"  chloride  of  lime "  (bleaching  powder)  may  be  mentioned. 
The  commercial  process  was  designed  by  Thenard  in  1799  and 
carried  out  by  Tennant  &  Co.  in  England.  About  the  same 
time  Berthollet  introduced  his  "Eau  de  Javelle "  (aqueous 
sodium  hypochlorite).  It  may  be  remarked  that  the  constitu- 
tion of  bleaching  powder  was  quite  unknown  till  about  1835, 
when  Balard  suggested  the  formula  CaCl(OCl). 

Turning  to  the  more  common  organic  products,  we  find  that 
alcohol  ("spirits  of  wine,"  "aqua  vitae  ")  has  been  obtained 
from  wines  from  the  earliest  times  by  simple  redistillation, 
though  in  this  way  it  never  attained  a  strength  of  more  than 


THE  APPLICATION  OF  CHEMISTRY          161 

92  per  cent.  During  the  past  century,  and  more  particularly 
since  about  1875,  when  the  phylloxera  began  to  increase  its 
ravages  amongst  vines,  beet-sugar  and  potatoes  have  been  the 
source  of  most  of  the  alcohol  supply.  Still-heads  for  im- 
proving the  fractionation  process  are  due  to  Argand,  Adam, 
and  Blumenthal ;  Gay-Lussac  systematized  alcohol  analysis 
("  alcoholometry  ")  in  1824. 

The  essences  or  ethereal  oils  (in  many  cases  ethyl  esters) 
have  always  formed  a  branch  of  chemical  industry,  but  as  the 
improvements  deal  chiefly  with  mechanical  appliances  for  ex- 
pressing or  distilling  the  different  plant-juices,  we  will  merely 
remark  here  that  Vaudin  introduced  vacuum  distillation  into 
essence  works  in  1879,  and  that  since  1885  Schimmel  & 
Co.  have  been  the  pioneers  in  this  branch  of  the  technical 
science. 

Vinegar  used  to  be  made  from  alcohol  by  Boerhave's  fer- 
mentation method  (1720),  known  as  the  "  slow  "  or  "  Orleans 
process";  in  1823  Schiitzenbach  and  Wagemann  introduced 
the  German  or  quick  vinegar  process.  Acetic  acid  itself  was 
first  made  on  a  large  scale  by  distillation  of  wood  by  the  patents 
of  Kestner  and  of  Halliday  (1848),  the  purification  of  the 
pyroligneous  acid  by  lime  being  due  to  Mallerot. 

Cane-sugar  came  originally  from  Asia  and  was  introduced  to 
Southern  Europe  and  Africa  by  the  Moors  ;  thence  it  was  trans- 
ferred to  the  Central  American  islands  by  the  Spanish  and 
Portuguese  colonists,  and  at  the  present  day  it  is  a  decaying 
industry  in  those  regions,  owing  to  the  introduction  of  beet- 
sugar.  The  presence  of  sugar  in  beet-juice  was  discovered  by 
Marggraf  in  1747,  but  the  first  technical  means  of  extracting  it 
were  found  by  Achard  in  1779.  The  first  factory  was  started 
in  France  in  1796,  and  until  about  1836  the  bulk  of  the 
beet-sugar  came  from  French  soil  ;  since  then,  however, 
Austria-Hungary,  and  especially  Germany,  have  taken  the  lead. 
Filtration  of  the  raw  juice  through  mineral  charcoal  was  intro- 
duced by  Figuier  (1811),  evaporation  of  the  syrup  under 
ii 


1 64         A  SHORT  HISTORY  OF  CHEMISTRY 

countries  since  the  seventeenth  century.  Of  improvements  in 
its  fabrication,  we  may  note  the  introduction  of  plate  glass  by 
de  Nehan  in  1688  (an  improved  process  was  devised  by  Pelou/e 
in  1856),  the  substitution  of  sand  projected  under  great  pres- 
sure for  hydrofluoric  acid  in  engraving  by  Tilghman  in  1870, 
and  the  advances  effected  by  Siemens  in  the  fusion  process. 
Modern  glass  usually  contains  much  more  soda  and  corre- 
spondingly less  lime  than  the  older  varieties.  In  1869  Em- 
merling  and  Bunsen  contributed  some  important  work  on  the 
solvent  action  of  water,  acids,  alkalies,  and  various  salts  on 
specific  kinds  of  glass.  The  phenomenon  of  devitrification  was 
first  observed  by  Reaumur,  about  1770. 

Earthenware,  again,  was  certainly  used  by  the  Chinese  as  well 
as  by  the  Egyptians,  but  pottery  impermeable  to  water  has  only 
been  known  since  the  eleventh  century  of  our  epoch,  while  the 
finer  kinds  of  earthenware  first  appeared  some  300  years  later 
(the  Moors  in  Spain,  and  the  Italians,  notably  L.  della  Robia, 
1411-1430)  ;  Palissy's  great  improvements  in  this  branch  took 
place  about  1550.  Porcelain  was  introduced  from  China  about 
1 600,  and  a  century  later  Morin  made  efforts  to  reproduce  the 
Chinese  excellence  at  Saint-Cloud  ;  Wedgwood  was  at  the  zenith 
of  his  fame  as  a  potter  about  1750,  and  a  decade  or  so  later 
the  famous  Sevres  porcelain  was  first  manufactured,  owing  to 
the  efforts  of  Reaumur,  Macquer,  and  others.  In  1800  Spode 
commenced  the  custom,  which  has  remained  practically  con- 
fined to  English  potteries,  of  substituting  bone  ash  for  a  part 
of  the  kaolin  or  clay  otherwise  used.  Of  recent  years  Seger 
(1892)  has  still  further  improved  the  manufacture  of  earthen- 
ware, and  much  research  has  been  carried  on  with  the  aim  of 
elucidating  the  chemical  structure  of  clays. 

There  is  not  a  great  deal  of  interest  attaching  to  the  history 
of  cements  ;  four  general  classes  are  recognized  at  the  present 
time :  lime,  Roman  cement,  Portland  cement  (which  is  an 
artificial  mixture  approximating  in  composition  to  the  older 
Roman  kind)  and  hydraulic  icements.  The  latter  require  the 


THE  APPLICATION  OF  CHEMISTRY         165 

addition  of  water  to  make  them  "set"  ;  they  were  introduced 
about  1 800  in  England  and  contain  lime  with  an  abundance 
of  alumina.  Improvements  in  hydraulic  mortars  were  made, 
notably  by  Winkler  and  Knapp,  a  few  years  ago  ;  theories  of 
the  manner  in  which  cements  "  set "  by  atmospheric  action 
have  been  discussed  during  the  past  quarter  of  a  century  by 
Le  Chatelier,  Newberry,  Rebuffot,  and  others. 

§  5.  Paper,  Matches,  Heat,  and  Light— The  use  of 
cotton  fabrics  for  paper  manufacture  did  not  commence  to 
supersede  the  old  papyrus  and  parchment  in  Europe  till  the 
eleventh  century,  although  in  China  it  was  used  long  previously. 
The  oldest  mark  on  cotton  paper  is  dated  A.D.  1050.  Paper 
manufacture  became  general  in  France  and  Bavaria  about 
1400,  but  all  paper  in  England  was  imported  until  1588.  In 
1750  Baskerville  produced  "vellum  paper".  Later  improve- 
ments may  be  summarized  as  follows  :  the  introduction  of 
machinery  (1803),  improved  by  Dickinson  (1809);  production 
from  different  trees  (palms,  bananas,  etc.)  (1839-1851);  pro- 
duction from  wood-pulp  or  straw  (1846),  rendered  practicable 
by  the  processes  of  Wolter  (1867),  Aussedot,  and  Tessie. 
Paper  used  to  be  bleached  by  chlorine  gas,  but  of  late  years  a 
better  and  safer  electrolytic  method  has  been  adopted. 

The  first  matches,  other  than  the  primitive  flint  and  tinder, 
were  made  of  .a  mixture  of  potassium  chlorate  and  sulphur 
("chemical  tinder,"  1807),  which  was  dipped  in  oil  of  vitriol 
to  effect  ignition.  Their  use  was  not,  it  is  believed,  very 
extended  !  In  1833  Romerand  Moldenhauer  introduced  phos- 
phorus matches,  while  the  original  form  of  the  modern  safety- 
match,  in  which  red  phosphorus  is  used  (and  usually  only  on 
the  prepared  surface  of  the  box),  dates  from  1848.  Of  late 
years  legislation  has  in  some  degree  helped  to  eliminate  the  older 
forms  of  poisonous  matches,  containing  yellow  phosphorus. 

A  very  important  modern  industry  is  that  of  india-rubber 
(first  introduced  into  Europe  in  1736),  the  raw  material  ema- 
nating chiefly  from  Para,  Peru,  Central  America,  and  the 


1 66        A  SHORT  HISTORY  OF  CHEMISTRY 

Congo.  The  most  interesting  development,  chemically  speak- 
ing, is  the  process  of  vulcanization  by  means  of  sulphur,  dis- 
covered by  Goodyear  in  1839.  Many  attempts  have  been 
made  to  effect  its  synthesis,  and  Harries  appears  recently  to 
have  succeeded. 

The  ancient  source  of  heat  for  domestic  purposes  was  wood, 
and  although  coal  was  known  to  the  Greeks  and  Romans  it  was 
not  greatly  used  as  a  combustible  until  towards  the  middle  of 
the  eighteenth  century,  when  the  introduction  of  machinery 
into  the  arts  created  a  demand  for  a  cheap  fuel.  Coke  was  first 
manufactured  in  1769.  It  is  almost  needless  to  point  to  the 
uses  made  of  coal-gas  and  electricity  for  heating  purposes 
during  the  last  fifty  years,  but  we  may  enumerate  a  few  gas 
fuels  used  for  technical  purposes  at  the  present  day,  such  as 
"producer  gas"  (CO  and  N2,  by  partial  burning  of  coal  in 
insufficient  air),  "  water-gas  "  (CO  and  H2,  by  blowing  steam 
over  red-hot  coke;  a  very  hot  flame,  useful  technically), 
"  mixed  gas  "  (CO,  H2  and  N2,  by  blowing  air  and  steam  over 
burning  coal;  cheap  and  hence  useful  in  small  works),  and 
"  Dowson  gas,"  which  is  practically  synonymous  with  the  last. 

The  problem  of  illumination  has  several  times  had  a  curiously 
beneficial  effect  by  indirectly  throwing  light  upon  purely  theo- 
retical questions.  A  commission  to  improve  the  means  of 
lighting  the  Paris  streets  turned  Lavoisier's  attention  to  the  sub- 
ject of  combustion,  and  again,  Dumas'  efforts  to  elucidate  the 
nature  of  annoying  fumes  emitted  by  chlorine-bleached  candles 
at  a  French  state  function  led  to  his  discovery  of  substitution 
in  organic  compounds.  Of  general  inquiries  into  the  nature  of 
luminosity,  Sir  H.  Davy's  (inventor  of  the  miner's  safety-lamp) 
and  Frankland's  have  been  most  useful.  With  regard  to  specific 
illuminants,  candles  made  from  tallow  (stearic  or  palmitic  acids 
from  fat  by  lime  or,  later,  sulphuric  acid)  and  subsequently  wax 
(solid  paraffins  and  plant  waxes)  come  first  in  chronological 
order.  Oils  of  varying  kinds  were  also  used — at  first  aromatic, 
scented  oils,  and  in  more  modern  times,  petroleum  from 


THE  APPLICATION  OF  CHEMISTRY          167 

Russian  or  American  wells.  At  present  the  distillation  of 
petroleum  ranks  second  in  importance  to  that  of  coal,  and 
yields  (in  descending  order  of  volatility)  gasolines  for  motor- 
engines,  petroleum  ether,  naptha  or  ligroin  for  lighting  and 
solvent  purposes,  machine-oils,  and  finally,  "  heavy  oils,"  semi- 
solid  greasy  materials  useful  as  lubricants.  Caucasian  petroleum 
is  made  up  mainly  of  hydroaromatic  hydrocarbons,  American  of 
aliphatic  or  paraffin  hydrocarbons. 

Finally  we  come  to  coal-gas,  introduced  in  1792  by  Murdoch, 
first  made  on  a  large  scale  six  years  later,  and  used  in  lighting 
London  streets  by  Winsor  in  1813.  Experiments  were  made 
intermittently  and  unsuccessfully  from  1800  to  1850  to  use 
cheaper  forms  of  gas,  such  as  oil-,  peat-,  or  water-gas.  Tech- 
nical improvements  in  coal  distillation  continued  to  be  made 
until  about  1880,  but  since  that  date  no  fundamental  change 
has  been  made  in  the  method  as  perfected  by  Lunge,  which, 
in  its  most  efficient  form,  permits  of  the  utilization  of  "  raw 
gases  "  (for  heating),  coal-gas,  gas-liquor  (source  of  ammonium 
salts  and  sulphides),  tar  (to  be  re-distilled)  and  coke  residue. 

The  distillation  of  the  coal-tar  (first  carried  out  by  Clayton 
in  1738  and  later,  in  France,  by  Lebrun  in  1786)  has  grown  to 
be  a  most  important  industry  ;  the  tar  itself  is  used  for  protect- 
ing iron,  wood,  ships,  etc.,  against  air  and  water,  as  an  artificial 
asphalte  (mixed  with  sand),  and  in  various  other  ways,  while 
its  distillation  products  include  benzene  and  many  other  aro- 
matic hydrocarbons  of  boiling-points  ranging  from  80°  to  300°  C, 
and  technically  important  substances  (especially  to  the  dye  in- 
dustries) such  as  phenol,  naphthalene,  anthracene,  pyridine, 
carbazole,  and  a  host  of  others. 

The  introduction  of  rare  earth  oxides  in  the  form  of  "  in- 
candescent "  mantles  is  due  to  Welsbach  (1885) ;  improvements 
both  in  the  composition  of  the  film  of  oxide  and  in  its  mechani- 
cal arrangement  continue  to  appear. 

§  6.  Dyes  —  Indigo,  madderwood  and  a  few  mineral 
colours  such  as  minium,  cinnabar,  rouge,  orpiment,  realgar  and 


1  68         A  SHORT  HISTORY  OF  CHEMISTRY 

galena  were  known  to  the  ancients,  judging  from  their  writings 
(e.g.  Pliny).  There  is  not  much  to  record  during  the  alchemistic 
period,  though  isolated  workers,  such  as  Glauber,  occasionally 
investigated  dyeing  processes.  The  use  of  mordants  (alum, 
iron  salts)  became  known  during  this  epoch,  but  their  precise 
mode  of  action  is  even  now  imperfectly  understood.  Macquer 
was  the  first  chemist  to  look  into  this  problem  (1795).  A 
table  showing  the  chief  mineral  and  other  dyes  manufactured  at 
the  opening  of  the  modern  era  may  be  useful  :  — 


Chetnical  Nature.  Artificial  Preparation. 

Cobalt  blue  (smalt)  1650  Schiirer  (fusion  of  glass 

and  cobalt  residues) 

Prussian  blue          Fe4[Fe(CN)6]3  1704  Diesbach 

Alizarin  1750  From  madder  plant  in 

Europe 

Zinc  white  ZnS  1790  Courtois 

White  lead  Pb(CO3)3  (basic)  1801  Th^nard 

Schweinfurt  green  Cu(C2H3O2)3,  3Cu(AsO2)2     1814  Sattler 
Ultramarine  From  sodium  silicates  and    1828  Guimet;  Gmelin  (for- 

sulphur  merly  from  lapis-lazuli) 

The  more  recent  history  of  organic  dyestuffs  is  bound  up,  as 
is  well  known,  with  the  exploitation  of  the  coal-tar  products. 
Faraday,  Laurent,  and  Runge  (1834)  are  prominent  among 
those  who  isolated  valuable  hydrocarbons  from  tar,  while  Hof- 
mann  (1843-5)  discovered  aniline  and  its  homologues  therein. 
In  1856  Perkin  obtained  mauve  (magenta)  by  the  oxidation  of 
aniline  with  chromic  acid,  and  since  then  innumerable  synthetic 
dyes  have  been  produced,  not  only  from  coal-tar  products 
(though  these  form  the  basis  of  the  most  widely-applied 
colours)  but  from  other  common  aromatic  substances  as  well. 
We  should  note  especially  the  device,  very  soon  introduced, 
of  improving  the  solubility  of  a  dye  by  increasing  its  acidity 
(sulphonation)  or  basicity  (alkylation).  The  evolution  of  the 
various  colouring  matters  can  best  be  grasped  by  a  chrono- 
logical table:  — 


THE  APPLICATION  OF  CHEMISTRY          169 


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i  yo         A  SHORT  HISTORY  OF  CHEMISTRY 

If  we  now  add  another  summary,  showing  the  theoretical 
development  of  the  formulae  of  the  various  parent  compounds 
concerned,  it  will  be  unnecessary  to  emphasize  further  the 
dependence  of  modern  industry  on  the  research  laboratory  : — 


Class  of  Substance.  Chief  Investigations. 

Aniline  and  homologues          1834  Mitscherlich  (C6H5NO2) ;  1834  Runge ;  1841  Zini 

1852  Bechamp(C6H3NH2) ;  1845  Hofmann  and  Mu 

pratt  ( p-Toluidine) 
Azo-bodies  Griess,  1859  (diazo  reaction) ;  1862  (diazoamidobenzem 

1866  (amidoazobenzene) 

Indigo  Constitution  by  Baeyer  and  his  students,  1865-1874 

Alizarin  Constitution  and  subsequent  synthesis  by  Graebe  ai 

Liebermann,  1868 

Acridine  Constitution  and  synthesis  by  Graebe  and  H.  Caro,  18' 

Triphenylmethane  Constitution   and  synthesis   by   Kekule  and   Franch 

mont,  1872 

Phenazine  Constitution  and  synthesis  by  Claus,  1873 

Phenthiazine  (thiodiphenyl-    Constitution  and  synthesis  by  Bernthsen,  1888 

amine) 

Phenoxazine  Constitution  and  synthesis  by  Bernthsen,  1887 

Flavones  and  Xanthones          Constitution  and  synthesis  by  St.  v.  Kostanecki,  A.  ( 

Perkin,  1895-1905 

§  7.  Explosives — Van  Helmont,  whose  explanations  of 
chemical  processes  have  several  times  attracted  attention  by 
their  clearness,  ascribed  the  characteristic  effect  of  exploding 
gunpowder  to  the  production  of  much  gas  ;  study  of  the  evolved 
gases  in  this  and  other  explosive  reactions  was  not  greatly  en- 
gaged in,  however,  until  the  nineteenth  century,  during  which 
their  composition  under  varying  conditions  was  made  the  sub- 
ject of  research  by  Debus,  Bunsen,  Abel,  Nobel,  and  others. 
Berthelot's  work  on  the  thermo-chemistry  of  explosives  is  very 
important. 

Of  the  individual  members  of  this  class  gunpowder  has  of 
course  been  longest  known,  having  been  employed  in  fireworks 
by  the  Chinese  and  Moors.  After  its  rediscovery  by  Schwarz 
in  1334  it  came  to  be  employed  in  warfare  by  the  occidental 


THE  APPLICATION  OF  CHEMISTRY          171 

nations.  It  has  remained  practically  the  only  explosive  in 
which  the  oxygen  necessary  for  combustion  is  supplied  by 
means  of  an  added  substance  (the  nitre),  unless  we  include  a 
disastrous  attempt  of  Berthollet's  (1786)  to  substitute  chlorate 
for  nitre. 

The  more  modern  type,  which  consists  usually  of  a  carbon 
compound  containing  sufficient  easily  available  oxygen  for 
complete  combustion,  includes  the  fulminates,  discovered  by 
Howard  (1800),  characterized  by  Liebig  and  introduced  as  de- 
tonators by  Ure  (1831) ;  the  picrates,  investigated  by  Fontaine, 
Designolles,  and  Abel ;  nitrocellulose  (gun-cotton),  discovered 
by  Braconnot  in  1823,  and  prepared  by  Schonbein  in  1846 
(Pelouze  (1838)  suggested  its  use  in  artillery,  but  much  difficulty 
was  found  in  manipulating  it  until  in  1886  Vieille  discovered 
the  secret  of  detonating  it  safely)  ;  and  nitroglycerine,  first 
produced  by  Sobrero  in  1847.  The  latter  was  first  applied  as 
dynamite  (after  absorption  in  kieselguhr)  in  1862  by  Nobel, 
Abel,  Champion,  and  others,  while  mixed  with  gun-cotton  it 
has  been  applied  by  these  chemists  and  others,  such  as  Vieille 
(1884),  to  the  fabrication  of  smokeless  powders  (e.g.  Nobel's 
mixture  (1890)  of  gun-cotton,  dynamite,  and  gelatine). 


CHAPTER  X 
THE  HISTORY  OF  PHYSICAL  CHEMISTRY 

WE  have  to  deal  in  this  chapter  with  the  direct  application  of 
physics  to  chemistry,  and  within  the  last  thirty  years  so  much 
progress  has  been  made  in  this  region  that  the  bulk  of  the  work 
which  we  shall  chronicle  will  have  been  carried  out  during  that 
period. 

At  the  outset  we  should  note  that  the  basis  of  the  whole 
science  rests  on  two  "  laws  " — the  conservation  of  mass  and  the 
conservation  of  energy. 

The  first  of  these  was  proved  by  Lavoisier  when  he  showed 
that  in  chemical  reactions  matter  is  never  either  created  or 
destroyed,  but  quite  recently  (1893-1908)  elaborate  experiments 
have  been  carried  out  by  H.  Landolt  in  order  to  test  how  far 
the  law  is  an  accurate  expression  of  fact,  the  final  result  being 
that  it  is  rigidly  correct  to  within  the  limits  of  one  part  in  ten 
million. 

The  accompanying  doctrine  of  the  conservation  of  energy  is 
due  more  to  Mayer  and  to  Joule  (1842)  than  to  any  other 
physicists,  though  not  a  few  workers  dealt  with  the  subject  in 
the  earlier  part  of  the  nineteenth  century. 

§  i.  The  Physical  Chemistry  of  Gases— The  first  to 
realize  the  varying  chemical  nature  of  different  gases  were  van 
Helmont  (who  introduced  the  term  "gas"  about  1620)  and 
Rey  (who  showed  that  air  possessed  weight  in  1630).  The 
relation  of  the  volume  of  gases  to  external  pressure  was  dis- 
covered by  Boyle  (1660)  and  Mariotte  (1670),  while  the  effect 

172 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY      173 

of  temperature  was  quantitatively  investigated  by  Charles  (1785) 
and  Gay-Lussac  (1808).  Dalton  (1807)  showed  that,  in  any 
mixture  of  gases,  each  exercised  its  own  "partial  pressure" 
independently  of  the  rest.  Again,  in  1808,  Gay-Lussac  found 
that  the  volumes  of  reacting  gases  always  bore  a  simple  ratio  to 
each  other  and  to  the  volume  of  the  products  (if  gaseous),  and 
this  served  in  certain  cases  to  contradict  Dalton's  atomic  hypo- 
thesis (cf.  p.  33)  until  in  1811  Avogadro  put  forward  the 
hypothesis  that  equal  volumes  of  gases  contained  equal  num- 
bers of  molecules  (Ampere  attempted  to  extend  the  same 
hypothesis  to  solids,  with  indifferent  success,  a  few  years 
later). 

In  the  meantime,  from  a  purely  physical  standpoint,  others 
were  developing  the  kinetic  theory  of  gases.  The  idea  that 
gas  particles  are  in  motion  was  expressed  by  Bernoulli  (1738) 
and  Herapath,  but  a  physical  estimation  of  their  mean  velocities 
was  first  made  by  Joule  in  1851.  The  modern  kinetic  theory 
of  gases  was  practically  stated  by  Waterson  (1845)  in  an  un- 
published paper  which  was  only  brought  to  light  in  1892  by 
Lord  Rayleigh,  and  consequently  the  fame  of  evolving  the 
theory  rests  with  Clausius  (1857)  and  Maxwell  (1860).  From 
this  in  1 88 1  van  der  Waals  constructed  a  modified  form  of  the 
"  gas  -equation  "  PV  =  RT  (Horstmann),  which  should  express 
the  deviations  from  Boyle's  and  Gay-Lussac's  laws  shown  by 
readily  liquefiable  gases,  and  also  to  a  smaller  extent  (Amagat, 
1880)  by  the  then-called  permanent  gases  (nitrogen,  hydro- 
gen, oxygen).  This  equation, 

\P  +  ~i)(v  ~  b)  =  RT  (where  a  and  b  are  specific  constants), 

is  so  accurate  an  expression  of  fact  that  by  its  means,  on  the 
one  hand,  Guye  and  Friedrich  were  able  in  1900  to  deduce 
practically  coincident  values  for  the  "  gas-constant  "  R  from 
measurements  of  different  gases,  and,  on  the  other,  Daniel  Ber- 
thelot  (1899)  has  theoretically  calculated  the  atomic  weights  of 


174         A  SHORT  HISTORY  OF  CHEMISTRY 

various  elements  from  the  densities  of  their  compounds  (or  of 
the  elements  themselves)  determined  by  Regnault  (1845),  Lord 
Rayleigh  (1888),  and  others.  The  values  so  obtained  agreed 
excellently  with  those  from  chemical  data. 

The  liquefaction  of  gases  was  a  subject  of  careful  study  by 
Northmore  (1805),  who  liquefied  chlorine,  and  by  Michael  Fara- 
day (1823),  who  condensed  ammonia,  sulphur  dioxide,  and  other 
gases  by  the  combined  application  of  considerable  pressure  and 
a  freezing  mixture.  His  principle  was  improved  by  later  workers, 
such  as  R.  Pictet  (1877),  Cailletet  (1877),  Wroblewski  and 
Olzscewski  (1883),  and,  finally,  Dewar  (1884),  by  increasing 
the  pressure  and  the  degree  of  cold,  so  that  all  the  known  gases 
(even  the  so-called  permanent  ones),  with  the  exception  of 
hydrogen  and  helium  (discovered  later),  had  been  liquefied  by 
1885.  Dewar  succeeded  in  liquefying  hydrogen  in  1898,  and 
in  the  meantime  a  new  principle  (Hampson-Linde,  1895,  the 
intense  cooling  of  a  gas  by  its  own  expansion  when  already 
cooled  under  great  pressure)  led  to  the  cheapening  of  liquefac- 
tion processes.  Finally,  H.  Kammerlingh  Onnes  condensed 
helium  in  1908  to  a  colourless  liquid  boiling  at  4'5°  Abs.,  and 
has  also  obtained  it  in  the  solid  state. 

In  1821  Cagniard  de  la  Tour  noticed  that  many  gases  could 
not  be  liquefied  above  a  certain  temperature  by  any  pressure, 
and  in  1869  Andrews  minutely  studied  the  phenomenon  and 
found  that  for  each  gas  there  existed  a  temperature  above  which 
no  amount  of  pressure  would  condense  it ;  he  called  this  the 
critical  temperature  and  the  pressure  necessary  to  produce  lique- 
faction at  that  temperature  the  critical  pressure,  while  the  specific 
volume  of  the  liquid  formed  was  the  critical  volume.  Much 
important  theoretical  work  has  since  been  carried  out  on  the 
critical  data,  notably  by  Mendelejew  (1884)  and  by  Ramsay  and 
Young  (1894). 

Finally  the  decomposition  of  some  gases  by  heat  and  their 
reformation  on  cooling  was  studied  by  Deville  in  1857  and 
named  "dissociation  ".  About  the  same  time  Kopp  and  Kekule 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     175 

observed  the  effect  and  set  it  down  to  partial  decomposition. 
Gaseous  dissociation  has  been  studied  quantitatively  by  methods 
of  effusion  (sal  ammoniac,  Pebal,  1862),  colorimetry  (phosphorus 
pentachloride,  Deville ;  nitric  peroxide,  Salet,  1868),  and  specific 
heat  (nitrogen  peroxide,  acetic  acid  vapour,  Berthelot  and 
Ogier,  1882). 

§  2.  Crystallography — This  sub-science,  so  important  for 
mineralogy,  was  given  a  definite  shape  by  Rome  de  L'Isle,  Hauy, 
and  Werner,  who  in  the  early  years  of  the  nineteenth  century 
classified  crystals  according  to  physical  form  and  assumed  that 
difference  in  form  entailed  difference  in  chemical  composition. 
This  was  overthrown  later  by  Mitscherlich's  discovery  of  poly- 
morphism (1821).  Later  crystal-systems,  by  means  of  which 
all  crystal-forms  were  finally  divided  into  thirty-two  geometrical 
classes,  are  due  to  Hessel  (1830),  Gadolin  (1867)  and  P.  Curie 
(1884). 

In  1888  Reinitzer  noticed  that  cholesteryl  benzoate,  before 
melting  to  a  clear  liquid,  passed  through  a  turbid  or  milky  phase, 
and  in  1890  other  instances  were  observed  by  Gattermann. 
Lehmann  (1890)  found  that  the  turbid  liquid  rotates  the  plane 
of  polarized  light,  and  must  therefore  be  doubly-refracting  and 
possess  crystalline  structure.  Such  substances  are  said  to  be 
liquid  crystals,  and  although  Tammann  (1901)  disputed  the 
crystalline  structure,  the  previous  explanation  is  usually  adopted 
at  the  present  time. 

The  relation  of  crystalline  form  to  chemical  composition  has 
naturally  been  the  subject  of  much  study.  In  1846  Buys-Ballot 
stated  that  the  elements  and  simpler  compounds  tended  to 
crystallize  in  the  simplest  forms  (regular  and  hexagonal)  and 
more  recently  Retgers  has  statistically  demonstrated  the  truth 
of  the  proposition  (1892).  Before  this,  however,  Mitscherlich 
discovered  isomorphism  (1819),  following  on  Gay-Lussac's  and 
Bendant's  observations  on  the  growth  of  potash  alum  in  am- 
monia alum,  and  of  ferrous  sulphate  in  copper  sulphate  solutions 
respectively.  Mitscherlich  based  his  views  of  isomorphism  on 


176         A  SHORT  HISTORY  OF  CHEMISTRY 

phosphoric  and  arsenic  acid  salts,  selenic  and  sulphuric  acid 
salts,  and  the  alums  and  oxides  of  iron,  chromium,  and  aluminium, 
and,  with  Berzelius,  held  that  isomorphous  bodies  contained 
similar  atomic  structures — a  point  utilized  by  Berzelius  to  assist 
in  determining  atomic  weights.  Fuchs,  similarly,  discussed  the 
constitution  of  isomorphous  minerals  (1872). 

Finally,  reference  must  be  made  to  Mitscherlich's  further  dis- 
coveries of  dimorphism  and  polymorphism  (1821),  and  to 
Scherer's  use  of  the  term  polymeric  isomorphism  (when  atoms 
had  been  replaced  by  an  atomic  group  to  form  an  isomorph). 
Kopp's  work  on  the  specific  volumes  of  isomorphs  is  note- 
worthy. 

Other  interesting  points  are  the  phenomenon  of  isogonism  or 
hemihedry  observed  by  Pasteur  in  1861,  wherein  the  slightest 
change  of  constitution  (change  of  asymmetric  configuration) 
causes  a  similar  change  in  the  position  of  the  crystal  facets,  and 
that  of  morphotropy,  studied  by  Groth  (1876) — the  definite 
alteration  of  form  caused  by  definite  substituents  in  organic 
compounds,  especially  in  the  aromatic  series. 

In  conclusion,  we  have  to  describe  the  comprehensive  theory 
recently  elaborated  by  Barlow  and  Pope  (1906),  who  "regard 
the  whole  of  the  volume  occupied  by  a  crystalline  structure  as 
partitioned  out  into  polyhedra,  which  lie  packed  together  in 
such  a  manner  as  to  fill  the  whole  of  that  volume  without  in- 
terstices. The  polyhedra  ...  are  termed  the  spheres  of 
atomic  influence  of  the  constituent  atoms."  The  crystalline 
forms  of  many  of  the  elements  and  simpler  compounds,  at  all 
events,  agree  with  the  postulates  of  this  theory,  which  is  also 
capable  of  furnishing  a  steric  formula  for  benzene  expressing, 
according  to  the  authors,  all  the  necessary  chemical  facts  (cf. 
chap.  vi.  p.  99). 

§  3.  Solutions — The  study  of  mechanism  of  solutions  has 
almost  always  been  developed  from  an  electrolytic  point  of  view, 
and  therefore  we  may  pass  over  the  earlier  history  of  this  branch 
by  referring  to  the  theories  of  electrolysis  dealt  with  in  chap,  iv., 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY      177 

§  4.  We  are  thus  left  with  the  discussion  of  the  osmotic 
pressure  of  solutions,  a  field  opened  up  by  the  work  of  Pfeffer 
(1877)  who  made  use  of  Traube's  "semi-permeable  mem- 
branes" (1867).  Pfeffer  found  that  substances  in  solutions 
obeyed  definite  laws  with  reference  to  their  osmotic  pressure, 
etc.,  but  it  was  van  5t  Hoff  who  first  perceived  that  dilute 
solutions  are  amenable  to  the  same  laws  as  gases,  and  that 
hence,  among  other  corollaries,  it  follows  that  the  molecular 
weight  of  a  dissolved  substance  is  related  to  the  vapour  pressure 
of  the  solution.  This  led  to  the  determination  of  molecular 
weights  by  lowering  the  vapour  pressure  of  a  solvent  (Raoult, 
1887)  or,  what  amounts  to  the  same,  lowering  of  freezing- 
point  or  elevation  of  boiling-point ;  it  then  appeared  that 
solutions  of  electrolytes  in  water  gave  abnormal  values  for  the 
molecular  weight,  and  this  found  an  explanation  in  Arrhenius' 
ionic  theory  (1886),  which  assumed  that  ions  exist  ready  formed 
in  dilute  solution,  the  electric  current  exerting  simply  a  directive 
effect.  This  does  not,  however,  afford  an  absolutely  perfect 
explanation,  and  it  seems  likely  that  the  final  theory  of  solutions 
will  be  a  combination  of  Mendelejew  and  Arrhenius'  theory  of 
hydration  of  ions  and  molecules  (1888)  for  concentrated  solu- 
tions, with  the  ionic  theory  for  dilute  solutions  and  electrolysis. 
The  electrical  conductivity  of  solutions  has  been  the  subject  of 
experiment  ever  since  Hittorf  (1853-9)  determined  the  "  trans- 
port numbers  "  for  the  migration  of  the  ions  and  Kohlrausch 
(1879)  discovered,  first,  the  relation  of  the  "  transport  number  " 
to  conductivity  (1879)  and  then  the  law  of  the  "  independent 
migration  of  the  ions"  (1885),  whereby  the  total  conductivity 
of  a  solution  was  shown  to  depend  upon  the  sum  of  the  two 
ionic  velocities.  The  conductivity  of  acids  (organic,  Ostwald, 
1878-87  ;  Walden,  1891  ;  very  weak  acids,  Walker,  1900)  has 
been  shown  to  be  a  measure  of  their  "relative  affinity,"  as 
already  described  (chap.  iv.  p.  57),  while  that  si  pure  water 
has  been  concordantly  determined  by  the  E.M.F.  of  an  acid- 
alkali  cell  (Ostwald,  1893),  the  hydrolysis  of  salts  (Arrhenius, 
12 


178         A  SHORT  HISTORY  OF  CHEMISTRY 

1893),  and  the  rate  of  hydrolysis  of  methyl  acetate  in  pure  water 
(van  't  Hoff  and  Wiis,  1893),  and  finally,  by  direct  measurement 
(Kohlrausch  and  Heyd wilier,  1894). 

Amphoteric  electrolytes  (both  acidic  and  basic,  such  as  methyl 
orange,  sulphanilic  acid,  glycocoll,  zinc  hydroxide  and  other 
feebly  acidic  metal  oxides)  have  been  studied  by  Kiister  (1892), 
Winkelblech  (1901),  J.  Walker  (1904),  and  many  others  ;  similar 
fields  have  been  opened  by  Hantzsch  in  the  case  of  psetido-acids 
ami  fasts  (iBgfyd  p.  104),  and  Noyes  and  Whitney  on  complex 
ions  ("double  salts")  in  1894. 

Conductivity  in  solvents  other  than  water  has  been  investi- 
gated by  Tessorin  (1896,  formic  acid),  Carrara  (1896,  acetone) 
and  especially  by  Jones  (1902-6)  and  by  Walden  (1901-6,  tetra 
ethylammonium  iodide  in  liquid  sulphur  dioxide,  sulphur  oxy- 
chloride,  ether,  etc.  etc.),  while  Kahlenberg  (1902-3)  has 
proved  that  the  dissociating  power  of  a  solvent  depends  directly 
upon  the  magnitude  of  its  dielectric  constant. 

Finally,  Nernst  has  recently  given  theoretical  explanations  of 
"  Volta's  pile  "  and  of  the  ordinary  galvanic  cells  by  means  of  a 
diffusion  theory  based  upon  van  't  Hoffs  theory  of  solutions. 

The  solutes  we  have  so  far  dealt  with  are  all  crystalline  sub- 
stances, but  we  must  now  refer  to  another  branch  of  soluble 
bodies,  the  colloidal  substances.  The  purification  of  these  has 
been  rendered  possible  by  the  process  of  dialysis,  discovered  by 
Graham  in  his  researches  on  diffusion. 

The  phenomenon  of  diffusion  seems  to  have  been  first  noticed 
by  Parrot  in  1815,  and  a  mathematical  treatment  of  the  subject 
appeared  by  Ficks  in  1855.  In  the  meantime  the  different 
rates  of  diffusion  and  effusion  of  gases  had  been  studied  by 
Graham  in  1851,  and  later  the  same  chemist  extended  his  ob- 
servations to  the  diffusion  of  dissolved  bodies  through  animal 
membranes.  He  found  that  these  were  permeable  to  one  set 
of  substances  (crystalloids)  and  impermeable  to  others  such  as 
dextrin,  silicic  acid,  tannin,  which  he  termed  colloids  (1862). 
Work  on  osmosis  by  Jolly,  Briicke,  and  Pfeffer  (1877)  proved 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     179 

that  the  osmotic  pressure  of  such  bodies  was  very  small,  and 
consequently  their  molecular  weight  should  be  enormously  large, 
that  of  many  being  greater  than  10,000  (Linebarger  found  by 
osmotic  pressure  measurements  in  1892  that  tungstic  acid,  one 
of  the  simpler  colloids,  possessed  a  molecular  weight  of  1700- 
1720;  (H2WO4)7  =  1750).  Much  work  has  been  done  of  late 
years  on  this  subject  (especially  by  Bredig,  1903,  and  Billitzer, 
1903),  but  the  structure  of  colloids  remains  very  uncertain  indeed 
and  we  will  therefore  simply  recall  Sabarejew's  division  of  col- 
loids (1891)  into  those  of  molecular  weight  greater  than 
30,000  (starch,  silicic  acid,  iron  hydroxide,  etc.),  and  less  than 
30,000  (dextrin,  tannin,  molybdic  acid,  etc.). 

§  4.  Molecular  Weight  Determination — It  may  be  use- 
ful to  give  a  summary  of  the  physical  methods  lately  developed 
for  its  estimation  of  molecular  weight ;  these  depend  mainly  on 
determination  of  vapour  density  or  of  osmotic  pressure  (direct  or 
indirect). 

(a)  Vapour  Density  Methods. — The  theory  of  these  methods 
depends  of  course  mainly  upon  the  application  of  Avogadro's 
hypothesis;  it  must  be  remembered,  however,  that,  while  in 
former  times  the  approximate  determination  of  vapour  density 
was  made  to  serve  as  a  check  on  the  multiple  of  the  chemically- 
determined  equivalent  which  was  to  be  accepted  as  the  true 
atomic  or  molecular  weight  (Cannizzaro,  1858),  more  recently 
the  application  of  van  der  Waal's  equation  (D.  Berthelot,  1899) 
has  led  to  exact  determinations  of  molecular  weight  by  gas 
density  in  numerous  instances. 

Four  different  principles  have  been  utilized  in  succession  for 
the  experimental  determination  of  vapour  density  : — 

Measurement  of  the  weight  of  a  given  volume  of  an  already 
gaseous  substance  (Regnault,  1845;  Lord  Rayleigh,  1888-; 
Leduc,  1892-8;  Morley,  1895). 

Measurement  of  the  weight  of  a  given  volume  of  vapour 
(Dumas,  1827  ;  applied  by  Dumas  and  by  Mitscherlich  to  the 
elements  sulphur,  arsenic,  phosphorus  and  mercury). 


i8o        A  SHORT  HISTORY  OF  CHEMISTRY 

Measurement  of  the  volume  of  a  given  weight  [Hofmann, 
1868,  designed  an  improved  form  of  Gay-Lussac's  apparatus 
(1801),  which  was  further  modified  for  high  temperature  work  by 
Ramsay  and  Young  (1885)]. 

Measurement  of  the  volume  of  air  (at  atmospheric  tempera- 
ture and  pressure)  displaced  by  the  vapour  from  a  given  weight 
of  substance  (Victor  Meyer,  1878).  This  has  been  found  to  be 
most  generally  applicable,  especially  for  very  high  temperatures 
(up  to  1900°  C.,  Biltz,  1896;  1700°  C,  Nilsonand  Pettersen, 
1889).  By  this  means  the  atomic  weights  of  silicon,  beryllium, 
thorium  and  germanium,  amongst  others,  have  been  established 
from  the  vapour  densities  of  their  chlorides,  while  the  dissocia- 
tion of  compounds  like  aluminium1  chloride  (A12C1G)  and  stannous 
chloride  (Sn2Cl4)  into  simpler  molecules  has  also  been  studied 
(V.  Meyer,  Nilson  and  Pettersen). 

(b)  Osmotic  Pressure  Methods. — The  discovery  of  the  con- 
nexion between  osmotic  pressure  and  molecular  weight  was  re- 
corded in  the  last  paragraph,  and  some  account  will  now  be 
given  of  the  practical  application  of  the  principle.  Guldberg 
(1870)  and  van  't  Hoff  (1886)  independently  deduced  from  the 
laws  of  vapour  pressure  that  the  depression  of  freezing-point 
and  elevation  of  boiling-point  were  both  proportional  to  altera- 
tions of  vapour  pressure,  and  it  appeared  later  that  both  depend 
on  the  osmotic  pressure,  and  hence,  on  the  molecular  weight  of 
the  solute.  This  led  to  four  new  methods  of  molecular  weight 
estimation : — 

(i)  Direct  Measurement  of  Osmotic  Pressure  of  Solutions. — 
This  is  chiefly  of  theoretical  interest,  since  it  is  difficult  to 
obtain  a  great  degree  of  accuracy.  Pfeffer  (1877)  used  semi- 
permeable  membranes  of  cupric  ferrocyanide,  Tammann  (1888) 
utilized  drops  of  potassium  ferro-cyanide  in  copper  sulphate 
solution,  and  de  Vries  (1888)  taught  how  to  prepare  isotonic  solu- 
tions by  observation  of  the  behaviour  of  certain  plant-cells  therein 
(plasmolysis),  and  obtained  in  this  way  a  good  determination  of 
the  molecular  weight  of  raffinose  (C18H32O16). 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     181 

The  Earl  of  Berkeley  and  Hartley  (1906)  have  recently  made 
important  additions  to  the  knowledge  of  osmotic  pressure, 
(ii)   Indirect  Measurement  of  Osmotic  Pressure  of  Solutions.— 

1.  Lowering  of  vapour-pressure  of  solvent  (Raoult,    1887; 
also  difficult  to  manipulate  with  sufficient  accuracy). 

2.  Depression  of  freezing-point  of  solvent.     Blagden  (i  788) 
and  Riidorff  (1861)  noticed  that  the  depression  was  proportional 
to   the  amount  of  dissolved   substance;   Coppet    (1871)    and 
Raoult  (1882)  saw  that  molecular  amounts  of  different  solutes 
depressed  the  freezing-points  of  a  given  solvent  to  the  same 
extent;    Beckmann  (1888)  devised  a  convenient  form  of  ap- 
paratus with  a  specially  delicate  thermometer,  in  both  of  which 
sundry  alterations  have  been  made  by  later  workers  ;  and  Ver- 
net   and  Abegg  (1894)  further  developed   the    mathematical 
theory  of  the  process. 

3.  Elevation  of  boiling-point  of  solvent  (Beckmann,  1889). 
The  last  two  methods  have  found  a  great  sphere  of  utility. 

§  5.  Relation  of  Physical  Properties  to  Chemical  Con- 
stitution :  (a)  Mechanical — Here  we  have  to  deal  once 
more  with  a  problem  whose  general  importance  has  only  been 
realized  within  the  last  twenty  or  thirty  years,  namely,  the 
dependence  of  the  physical  properties  upon  the  constitution  of 
compounds.  It  is  now,  however,  generally  admitted  that  this 
is  a  subject  of  extreme  importance  to  the  development  of 
theoretical  chemistry.  A  definite  systematization  of  such  pro- 
perties was  not  known  until  Ostwald  in  1891  defined  them  as 
additive,  depending  simply  on  the  atomic  composition  of  the 
molecule — mass  is  the  only  perfect  example — constitutive  (in- 
fluenced by  the  mode  of  union  of  the  atoms — optical  activity 
and  absorption  spectra  are  perhaps  the  most  striking  instances) 
and  colligative  (depending  on  the  number  of  molecules — vapour 
density,  osmotic  pressure,  etc.). 

We  shall  now  proceed  to  give  a  very  brief  and  necessarily 
incomplete  resume  of  the  development  of  the  present  views  on 
different  types  of  properties,  and  will  commence  with  those 


i8a         A  SHORT  HISTORY  OF  CHEMISTRY 

which,  for  want  of  a  better  name,  may  be  called  mechanical 
properties. 

(a)  Specific  Gravity ;  Specific  a?id  Molecular  Volume. — The 
methods  devised  by  physicists  for  measuring  the  density  of  gases 
have  already  been  summarized  ;  the  specific  gravity  of  liquids 
used  to  be  generally  measured  by  the  specific  gravity  bottle, 
but  more  refined  methods  have  been  introduced  by  Sprengel 
and  Ostwald  (1873,  the  pycnometer),  and  by  Kohlrausch  and 
Holhvachs  (1894,  the  areometric  method,  based  on  Archimedes' 
principle).  The  density  of  solids  is  not  so  easy  to  obtain  with 
perfect  accuracy,  but  the  principles  chiefly  used  have  been  that 
due  originally  to  Archimedes,  and  that  whereby  the  solid  is 
made  to  swim  free  in  a  liquid  mixture,  whose  composition 
is  suitably  adjusted  by  means  of  a  heavy  component  (e.g. 
methylene  iodide)  and  a  light  component  (e.g.  benzene).  This 
device  was  brought  to  a  high  degree  of  perfection  by  Retgers 
in  1889. 

The  specific  volumes  of  elements  and  compounds  were  first 
systematically  studied  by  Kopp  (1842-1855),  who  claimed  that 
it  was  a  purely  additive  function.  Later  work  by  Schroder 
(1880),  Lossen  (1882),  Horstmann  (i 886-8),  and  others,  not- 
ably Traube,  has  shown  that  although  Kopp's  view  is  roughly 
correct,  definite  modifications  are  introduced  by  constitutional 
influences.  Researches  on  the  specific  gravity  of  liquid  mixtures 
(Linebarger,  1896)  have  also  proved  interesting,  since  in  many 
cases  evidences  of  "  association  "  or  loose  molecular  combination 
have  been  found. 

(If)  Surface  Tension. — The  phenomena  of  capillarity  were  ex- 
plained by  Young  in  1804,  and  attention  has  frequently  been 
paid  to  the  property  since,  its  measurement  having  been  effected 
by  Laplace,  Gay-Lussac,  J.  Traube  (1891),  van  der  Waals  (1894), 

and    others.     The    temperature   coefficient      J       has    been 

shown  to  be  constant  for  nearly  related  members  of  the  same 
homologous  series  and  its  utility  as  a  means  of  testing  the 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     183 

molecular  complexity  of  liquids  has  been    proved  by  Eotvos 
(1886),  and  by  Ramsay  and  Shields  (1893). 

(c)  Internal  Friction. — The  viscosity  of  gases  has  been  chiefly 
studied,    from   a    physico-chemical    standpoint,   by  L.  Meyer 
(1879),  and  Staedel  (1882),  while  much  work  has  been  done 
with  respect  to  solutions  by  Ostwald  (1891),  who  designed  a 
convenient  viscometer,  and  to  liquids  by  Thorpe  and  Rodger 
(1894-6),  and  to  liquid  mixtures  of  many  types  by  Dunstan 
(1904  onwards)  and   his   students,    and   in  lesser  degree  by 
numerous  other  workers.     The  fact  that  molecular  association 
can  take  place  in  solid  as  well  as  in  liquid  mixtures  has  been 
shown  by  Trouton  and  Dunstan  (1908)  in  the  case  of  certain 
alloys,  the  method  used  being  the  stretching  of  a  wire  of  the 
substance  in  question  by  a  given  weight. 

(d)  Melting-point. — Attempts  have  from  time  to  time  been 
made  to  give  quantitative  rules  for  melting-  and  boiling-points, 
but  with  very  little  success.     The  most  notable  regularities 
are  that  the  property  is  affected  very  little  by  pressure  (Kelvin, 
1850) ;  that  several  series  of  organic  acids  are  characterized  by 
the  melting-points  of  the  odd  members  of  the  series  lying  on 
one  curve,  while  those  of  the  even  members  are  on  another 
(Baeyer,  1877) ;  that  in  aromatic  compounds,  nitro-substituents 
melt  higher  than  bromo-derivatives,  and  these,  again,  higher 
than  the  corresponding  chloro-bodies  (Petersen,  1874),  and  a 
para-substituted  compound  melts  in  general  higher  than  either 
the  meta-  or  ortho-derivative  (Beilstein,  1886). 

The  only  accurate  methods  of  melting-point  determination 
are  the  immersion  of  a  delicate  thermometer  in  a  large  amount 
of  the  heated  solid,  or  of  the  super-cooled  liquid  (Landolt,  1888). 

(e)  Boiling-point. — Kopp  sought  to  show  that  equal  differ- 
ences in  constitution  produce  equal  differences  in  boiling-point 
(1845),  but  soon  found  that  this  was  a  very  limited  rule.     Re- 
gularities have  been  found  also  by  Tollens  (1869),  Marckwald 
(1888),  Henry  (1888),  Earp  (1893),  and  others;  the   general 
result  being : — 


184         A  SHORT  HISTORY  OF  CHEMISTRY 

(i)  Increase  of  molecular  weight  tends  to  increase  the  boiling- 
point. 

(ii)  In  organic  isomers,  the  normal  compound  has  the 
highest,  and  the  most  compactly  arranged  molecule  the  lowest 
boiling-point. 

(iii)  A  substituent  in  a  central  position  in  the  molecule 
tends  to  volatility. 

In  1891  Vernon  suggested  that  many  irregularities  were  due 
to  polymerization  and  from  the  behaviour  of  different  series 
estimated  the  degree  of  polymerization  of  water,  sulphuric  acid, 
sulphur,  and  other  substances  from  their  boiling-points.  The 
relation  between  boiling-point  and  critical  temperature  was 
made  clear  by  Thorpe  and  Riicker  (1884). 

§  6.  Relation  of  Physical  Properties  to  Chemical 
Constitution  :  (H)  Electrical — We  have  already  discussed 
the  most  important  electrical  property  (conductivity)  in  con- 
nexion with  the  history  of  electrolysis  (pp.  56ff.),  and  we  only 
need  refer  here  to  the  study  of  magnetism  and  of  di-electric 
constant.  The  former  has  been  studied  by  Pliicker  (1857)  and 
by  Henrichsen  (1888)  who  found  that  all  the  organic  com- 
pounds he  examined  were  diamagnetic  and  that  the  property 
was  mainly  additive,  although  the  ethylenic  linking,  —  C  :  C  — , 
exerted  abnormal  influence.  Jager  and  St.  Meyer  (1897) 
examined  the  magnetism  of  elements  in  compounds,  more 
particularly  those  of  chromium,  iron,  and  manganese. 

Measurements  of  di-electric  constant  have  been  carried  out 
by  Silow  (1875)  by  the  electrometer,  by  Nernst  (1893)  by  the 
condenser  method,  and  by  Drude  (1897)  by  means  of  stationary 
electric  waves.  The  latter  physicist  and  Walden  (1906)  have 
carried  out  extensive  work  on  the  di-electric  constants  of  many 
organic  compounds.  Kahlenberg  (1903)  showed  that  the  dis- 
sociating power  of  a  solvent  upon  electrolytes  was  connected 
with  the  dielectric  constant. 

Thermal  properties  (specific  heat,  etc.)  will  be  considered  in 
§  9  of  this  chapter. 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     185 

§  7.  Relation  of  Physical  Properties  to  Chemical 
Constitution  :  (c)  Optical — The  history  of  optical  activity 
having  already  received  attention  (p.  in),  we  will  pass  on  to 
that  of— 

(a)  Refractive  Power. — The  property  of  refraction  of  light, 
known  to  physicists  for  a  very  long  time,  has  more  recently 
been  found  to  be  one  of  the  most  useful  physical  guides  to 
chemical  constitution.  The  earlier  workers  from  a  chemical 
standpoint  include  Cahours  and  Deville ;  the  first  formula  for 

molecular  refractive  power  \—r(n  —  1))  was   put   forward  by 

Gladstone  and  Dale  in  1858  (Landolt,   1864);  a  second  and 

/M     «2  -  1\ 

more  correct  expression  ( —  .  -5 s  I  was  deduced  theoretic- 

\d     ri*  +  2/ 

ally  and  confirmed  practically  by  Lorenz  and  Lorentz  in  1880. 
Since  1880  the  most  prominent,  but  by  no  means  the  only, 
worker  in  the  field  has  been  Briihl,  who  has  shown  that  the 
property  is  sufficiently  additive  to  admit  of  calculation,  since 
the  constitutive  influences  are  so  regular  that  numerical  values 
may  in  general  be  assigned  to  them.  When,  however,  two 
unsaturated  groups  occur  side  by  side  in  the  molecule  anom- 
alous refractivities  are  observed,  and  this  is  accounted  for  by 
Briihl  as  being  due  to  the  "  conjugation  "  of  two  groups  rich 
in  residual  affinity.  Briihl  has  also  been  a  notable  worker  in 
connexion  with  molecular  dispersion  of  light,  a  property  found 
to  be  more  constitutive  than  refractive  power. 

(b)  Magnetic  Rotation. — In  1846  Faraday  discovered  that 
any  transparent  substance  in  a  magnetic  field  deflects  the  plane 
of  vibration  of  polarized  light.  This  property  has  been  very 
thoroughly  studied  by  Sir  W.  H.  Perkin,  who  defined  specific 
and  molecular  magnetic  rotatory  power,  and  found  the  property 
to  be  mainly  additive,  but  in  a  small  degree  constitutive,  and 
showing  anomalous  values  in  the  case  of  conjugated  unsaturated 
systems.  There  have  been  few  other  prominent  workers  in 


186         A  SHORT  HISTORY  OF  CHEMISTRY 

this  section,  but  we  may  refer  to  Jahn's  study  of  the  additive 
properties  of  the  magnetic  rotatory  powers  of  ions  (1891). 

(c)  Spectroscopy. — As  long  ago  as  the  middle  of  the  eighteenth 
century  the  distinction  of  sodium  from  potassium  salts  by  means 
of  their  flame-colorations  was  known  to  Marggraf  and  to 
Scheele,  but  more  systematic  examination  of  the  spectrum  was 
entered  upon  by  Wollaston  (1802),  Herschel  (1822),  and  others. 
The  spectra  of  coloured  flames  were  also  studied  by  Miller 
(1845),  Swan  (1856),  and  others,  but  it  was  not  till  1859  that 
Kirchhoff  and  Bunsen  established  the  law  that  each  chemical 
element  has  its  own  characteristic  spectrum.  From  that  time 
the  discovery  of  new  elements  by  the  spectroscope  has  been 
effected  by  Bunsen,  Crookes,  Lockyer,  Ramsay,  and  others, 
while  various  types  of  emission  spectra  (spark,  arc,  and  phos- 
phorescent) have  been  pressed  into  service.  In  1863  Roscoe 
and  Clifton  discussed  the  alteration  of  the  spectrum  of  a  sub- 
stance by  varying  physical  conditions  and  by  change  of  consti- 
tution. On  the  other  hand,  mathematical  relations  of  the 
spectral  lines  were  sought  for  by  Stoney  (1871),  Maxwell  (1875), 
Lecoq  de  Boisbaudran  (1889),  and  Rowland  (1893-),  and  the 
regular  formation  of  some  elementary  spectra  began  to  appear 
evident.  In  1885  Balmer  produced  a  formula  by  which  to 
calculate  the  hydrogen  spectrum,  and  in  1891  Kayser  and 
Runge  gave  similar  expressions,  but  not  quite  so  successfully, 
for  some  of  the  metals.  Twelve  years  later  Riecke  suggested 
an  analogy  between  the  lines  of  a  spectrum  and  the  harmonic 
vibrations  of  sound,  and  in  1 906  Stark  by  an  extension  of  the 
idea  conceived  the  lines  as  the  expression  of  electronic  vibration 
and  deduced  various  electronic  "  atomic  "  formulae  therefrom. 
Such,  briefly,  is  the  development  of  our  knowledge  of  the  con- 
stitution of  spectra — a  line  of  research  which  by  co-ordinating 
optical  properties  with  the  electronic  theory  of  matter  may 
possibly  in  course  of  time  furnish  an  explanation  of  the  inter- 
dependence of  physical  properties  and  chemical  constitution. 

Another  equally  fruitful  field  has  been  found  in  absorption 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     187 

spectra.  Wollaston  (1802)  and  Fraunhofer  (1814)  noticed  the 
first  case  of  this  in  examining  the  solar  spectrum,  and  with  their 
work  as  basis,  astronomy  has  been  able  to  determine  the 
qualitative  composition  of  many  of  the  stars  and  planets. 

The  absorption  spectra  of  solutions  of  electrolytes  and  of 
organic  compounds  have  engaged  numerous  chemists,  of  whom 
we  have  only  space  to  mention  a  few.  Ostwald  and  others 
have  shown  that  in  dilute  solutions  each  ion  has  its  own  definite 
spectrum.  The  work  on  organic  compounds  concerns  more 
particularly  the  ultra-violet,  invisible  part  of  the  spectrum,  and 
has  been  carried  out  by  Kriiss  (1883-8),  Vogel  (1891),  Hartley 
and  Dobbie  (1899),  Baly  and  co-workers  (1905),  and  many 
others.  Most  of  the  research  has  been  done  in  endeavours  to 
follow  constitutional  change  by  means  of  the  property. 

An  interesting  practical  application  is  that  made  by  Witt 
(1876),  Nietzski  (1879),  and  others,  who  have  based  theories  of 
colouring  and  dyeing  upon  their  observations.  Witt  introduced 
the  conception  of  chromophores  or  colour-producing  groups  and 
chromogens  or  groups  which  must  be  attached  to  a  chromophore 
before  the  characteristic  colour  is  exhibited.  Schiitze  (1892) 
traced  a  connexion  between  colour  and  increasing  molecular 
weight. 

(d)  Fluorescence  has  been  found  to  be  almost  as  constitutive 
a  property  as  absorption  spectra  or  optical  activity.  Notable 
names  in  connexion  with  this  property  are  R.  Meyer  (1897), 
KaufTmann,  and  Kehrmann.  Kauffmann  applied  to  fluorescence 
a  similar  explanation  (of  "  fluorophores  "  and  "  fluorogens  ")  to 
that  of  colour  given  by  Witt,  and,  further,  has  found  a  relation 
between  the  property  and  the  disposition  of  "  partial  valencies," 
while  Hewitt  (1900)  has  observed  that  in  very  many  cases 
fluorescence  is  accompanied  by  a  possibility  of  "  double  sym- 
metrical "  tautomerism  in  the  molecule,  and  suggests  that  the 
phenomenon  is  connected  with  molecular  vibration  due  to  such 
dynamic  isomerism. 

§  8.  Photo-chemistry — The  chemical  action  of  the  ultra- 


i88         A  SHORT  HISTORY  OF  CHEMISTRY 

violet  rays  of  light  is  important  both  in  its  connexion  with 
modern  theory  and  in  its  practical  applications  in  the  direction 
of  photography,  etc.  Dealing  with  the  latter  aspect  first,  it 
would  seem  as  though  the  darkening  of  silver  salts  was  known 
to  Boyle  (who  set  it  down  to  atmospheric  influences),  while 
Schultze  a  few  years  later  declared  the  effect  to  be  produced  by 
light.  Scheele  examined  the  effect  of  the  solar  spectrum  in 
detail  and  found  the  action  to  be  concentrated  in  the  violet 
part,  and,  finally,  Ritter  in  1801  ascribed  it  to  the  ultra-violet 
rays.  The  development  of  photography,  after  its  initiation 
by  Daguerre  and  Talbot  in  1839,  was  especially  furthered  by 
Niepce  (collodion  films,  1847),  Bennett  (bro mo-gelatine  films, 
1878),  and  Lippmann  (colour  photography,  1892). 

In  the  meantime  other  actinic  chemical  reactions  were  brought 
to  light,  especially  by  Davy  and  Faraday  (union  of  CO  and 
C12 ;  H2  and  C12 ;  chlorination  of  marsh-gas,  etc.),  and  a  de- 
tailed study  of  the  mechanism  of  the  process  was  made  by 
Bunsen  and  Roscoe  (1857).  Their  results  showed  that  such 
actions  were  supported  by  certain  light-waves  in  the  ultra- 
violet region,  which  in  this  way  supplied  the  necessary  energy 
for  the  change.  That  energy  was  given  up  by  the  waves  in 
question  followed  from  the  fact  that  a  given  stream  of  the  rays 
lost  all  capacity  for  chemical  action  after  passing  through,  for 
example,  a  mixture  of  hydrogen  and  chlorine  {photo-chemical 
extinction). 

It  was  also  noticed  that  the  action  of  light  usually  commenced 
very  sluggishly  and  then  rose  to  a  maximum  {photo-chemical 
induction)  ;  this  was  explained  subsequently  on  the  hypothesis 
that  an  intermediate  product  was  first  formed  which  was  itself 
responsible  for  the  final  more  rapid  rate  of  change.  (Burgess 
and  Chapman,  1904,  and  Wildemann,  1902.)  A  similar  prin- 
ciple to  this  (the  "  latent  action  "  of  light)  forms  the  basis 
of  the  developing  process,  which  has  been  explained  as  being 
set  up  by  the  particles  of  metallic  silver  or  of  silver  sub- 
halide  (Luther,  1899)  produced  in  the  first  momentary  ex- 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     189 

posure.  Subsequent  improvements  in  developing,  toning, 
fixing,  etc.,  have  followed  as  new  organic  reagents  suitable 
to  these  purposes  have  been  synthesized. 

Other  more  recent  examples  of  actinic  action  are  the  decom- 
position of  various  acids  (succinic,  tartaric,  etc.)  by  sunlight  into 
carbon  dioxide  and  simpler  acids  in  presence  of  uranium  oxide 
(see  Kamp,  1893),  and  the  synthesis  of  indigo  from  an  ethereal 
solution  of  benzal-0-nitroacetophenone  in  sunlight  (Engler  and 
Dorant,  1895). 

§  9.  Thermo-chemistry — We  have  to  deal  here  mainly 
with  the  relations  to  chemistry  of  specific  heat,  latent  heat,  and 
heat  of  reaction. 

(a)  Specific  Heat  of  Gases, — Measurements  of  the  specific  heat 
of  a  gas  at  constant  pressure  were  made  by  Delaroche  in  1811, 
but  more  accurately  by  Regnault  (1853)  and  Wiedemann  (1876). 
Regnault's  method  is  the  most  important  for  the  value  at  con- 
stant volume.  The  difference  in  the  values  (Cp  -  Cv  =  i  '99) 
has  been  used  by  physicists  (e.g.  Mayer,  1842)  to  determine  the 
mechanical  equivalent  of  heat,  but  to  chemists  the  ratio  Cp  :  Cv 
is  more  interesting,  since  this  has  been  proved  to  furnish  an 
indication  of  the  molecular  complexity  of  the  gas  in  question. 
Methods  for  the  direct  measurement  of  the  ratio  are  due  to 
Clement  and  Desormes  (adiabatic  expansion,  1815)  and  to 
Kundt  and  Warburg  (ratio  of  sound  wave-lengths  in  the 
experimental  and  in  a  known  gas,  1876).  The  most  famous 
applications  of  this  formula  are  for  the  monatomic  gases  mer- 
cury (vapour),  and  helium,  argon,  and  their  congeners. 
Measurements  of  the  specific  heat  of  gases  at  high  temperatures 
show  that  their  heat-capacity  remains  constant  up  to  2700°  C. 
(Le  Chatelier,  1881;  Berthelot  and  Vieille,  1884). 

(fr)  Specific  Heat  of  Elements  and  Compounds, — In  1818, 
Dulong  and  Petit  proved,  though  not  very  accurately,  that 
"  the  capacity  for  heat  of  many  atoms  is  the  same,"  namely, 

spec,  heat  x  atomic  weight  =  6*3 ; 
this   rule   was   seized    upon    by   Berzelius    as    a   method   of 


1 9o         A  SHORT  HISTORY  OF  CHEMISTRY 

checking  atomic  weights — a  sphere  in  which  it  has  proved 
exceedingly  useful,  although  at  first  more  credence  was  given 
to  deductions  from  isomorphism  than  from  specific-atomic 
heat.  Neumann  educed  a  similar  rule  for  compounds  in  1831, 
and  a  possibility  of  removing  some  of  the  discrepancies  of 
the  Dulong- Petit  law  appeared  when  Regnault  (1840),  Kopp 
(1864)  and  others  showed  that  specific  heat  in  many  cases 
varied  markedly  with  temperature.  Remeasurement  of  anomal- 
ous values  such  as  those  for  boron,  beryllium,  silicon  and  carbon, 
over  an  extended  upward  range  of  temperature  has,  in  the  hands 
of  Weber  (1875),  Nilsen  and  Pettersen  (1880),  and  Tilden 
(1905),  led  to  the  verification,  within  narrow  limits,  of  the 
Dulong-Petit  law. 

We  must  also  mention  work  on  the  specific  heat  of  liquids 
and  liquid  mixtures,  undertaken  with  a  view  to  finding  structural 
influences  ;  this  has,  however,  not  received  so  much  attention  as 
in  the  case  of  some  other  properties. 

(<r)  Latent  Heat. — The  property  of  latent  heat  has  been  less 
directly  connected  with  chemical  work  than  specific  heat,  but 
we  may  recall  that  it  was  discovered  by  Joseph  Black  in  1762 
and  that  Lavoisier  more  thoroughly  investigated  it.  The  de- 
terminations of  freezing-point  by  the  method  of  supercooling 
and  in  Beckmann's  depression  of  freezing-point  apparatus 
are  of  course  founded  on  the  development  of  latent  heat  in 
solidification. 

(d)  Heat  of  Chemical  Combination. — Employing  calorimetric 
methods  which  nowadays  appear  somewhat  crude,  Lavoisier  and 
Laplace,  and  also  Davy,  concluded  that  the  same  amount  of 
heat  is  evolved  in  decomposing  a  compound  as  is  absorbed  in 
synthesizing  it,  or  conversely,  according  to  whether  the  com- 
pound is  endo-  or  exo-thermic  (a  term  introduced  by  Berthelot, 
1865).  In  I84o  Hess  put  forward  what  are  known  as  his 
"  Laws  of  constant  heat  summation,"  stating  that  the  heat  of 
formation  or  reaction  of  a  given  chemical  system  is  always  the 
same,  and  thus  anticipating  the  deductions  made  from  the 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     191 

principle  of  the  conservation  of  energy  (mechanical  equivalent 
of  heat),  stated  a  few  years  later  by  Joule. 

Favre  and  Silbermann  (1853)  introduced  improvements  in 
the  calorimetric  measurements,  and  Andrews,  Graham,  and 
Marignac  are  notable  amongst  those  who  studied  thermo- 
chemistry after  Hess'  time.  The  most  far-reaching  work, 
however,  has  been  carried  out  by  Julius  Thomsen  (since  1853) 
and  by  Berthelot  (since  1865). 

Especially  noteworthy  are  their  observations  that  the  heat  of 
neutralization  of  any  strong  acid  by  any  strong  base  in  dilute 
solution  is  constant  (a  fact  made  clear  later  by  the  ionic  dis- 
sociation theory,  the  essential  reaction  being  in  all  cases 

+ 
H  +  OH  =  H2O  +  13700  calories),  and  their  attempts  to  throw 

light  upon  the  constitution  of  benzene  from  thermo-chemical 
data. 

§  10.  Electro-chemistry — We  may  refer  to  chap.  iii.  §  7 
for  the  history  of  the  electronic  theory,  and  the  various  theories 
of  electrolysis,  to  §  3  of  the  present  chapter  for  further  reference 
to  the  conductivity  of  solutions  and  the  theoretical  problems 
connected  with  galvanic  cells,  and  to  chap.  ix.  §  3  for  the 
application  of  electricity  to  metallurgy  and  technical  chemistry 
in  general. 

It  may  be  remarked  here,  however,  that  the  mathematical 
treatment  of  the  processes  of  galvanic  current  production  was 
commenced  by  Lord  Kelvin  (Sir  W.  Thomson)  and  worked 
out  by  Helmholtz,  van  't  Hoff,  Nernst  (1889)  and  others,  who 
have  applied  it,  not  only  to  the  simple  concentration -cell, 
but  to  the  more  complex  elements  of  the  common  forms  of 
galvanic  cells  and  to  accumulators. 

Of  recent  years  electrolytic  oxidation  and  reduction  has  re- 
ceived much  attention  in  view  of  the  possibility  of  preparing 
technically  valuable  organic  substances  thereby.  Haber  (1898) 
has  shown  that  the  reduction  of  nitro-benzene  can  be  carried 
to  practically  any  definite  degree  from  azoxybenzene  down  to 
aniline  by  regulation  of  the  cathode  potential,  while,  corre- 


192         A  SHORT  HISTORY  OF  CHEMISTRY 

spondingly,  Davy-Henault  (1900)  found  that,  according  to  the 
potential  at  the  anode,  aldehyde,  or  acetic  acid,  or  higher  pro- 
ducts could  be  more  or  less  quantitatively  obtained  by  the 
oxidation  of  alcohol. 

In  conclusion,  a  summary  of  the  theoretically  interesting 
electro-syntheses  of  the  simpler  organic  compounds  may  be 
useful  :  — 

Acetylene,  methane,  etc.  ;  Berthelot,  1868. 

Hydrocyanic  acid   (from  acetylene  and  nitrogen,  as  well  as  from 

cyanogen  and  hydrogen)  ;  Berthelot,  1868. 
Paraffins  from  fatty  acids  ;  Kolbe,  1849. 
defines  and  acetylenes  from  saturated  and  ethylenic  diabasic  acids 

(respectively)  ;  Kekule",  1864. 
Succinic  ester,  from  potassium  ethyl  malonate  ;  Crum  Brown  and 

J.  Walker,  1891. 
Ethane    tetracarboxylic    ester,   from    disodium    ethyl    malonate  ; 

Mulliken,  1895. 
Keten  from  acetic  anhydride  ;  Wilsmore  and  Stewart,  1907. 

§n.  Chemical  Statics  and  Dynamics  —  We  have  seen 
(chap.  iv.  §  i)  how  the  evolution  of  Wenzel's  and  Berthollet's 
views  on  chemical  affinity  led  to  Guldberg  and  Waage's  state- 
ment of  the  law  of  mass  action.  Since  their  time,  many  re- 
actions have  been  tested  with  reference  to  the  characteristic 
equation 


with  the  result  that  chemical  actions  have  become  susceptible 
to  mathematical  treatment. 

We  will  indicate  the  chief  instances  which  have  led  to  this 
state  of  affairs,  taking  first  of  all  the  case  in  which  the  reaction 
reaches  a  state  of  equilibrium,  represented  by  the  equation 

CiC,,  .  .  .  =  KCVC,,1  .  .  .  (chemical  statics). 

The  following  examples  have  served  to  point  out  the  truth  of 
this  law  :  — 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     193 

The  reaction  H2  +  I2  ^  2HI  Hautefeuille,  1867;  Lemoine,  1877. 

The  dissociation  N2O4  ^  2NOa  Natanson,  1885. 

*The  dissociation  S8  ^  S2  Biltz,  1888-1902. 
The  reaction  CaC03  =£= 


CaO] 

V 

O2     J 


Le  Chatelier,  1888. 
The  reaction  2CO2  ^  2CO  + 

Ester-formation     from    acid    and|  Berthelot  and  Pe"an  de  St.  Gilles, 

alcohol  /         1863. 

Mutual  solubility  of  liquids  I  Berthelot  and  Jungfleisch,  1872. 

Distribution   of   a    substance    be-  V  Nernst,  1891. 

tween  two  solvents  J  Hendrixson,  1897. 

The  methods  used  varied  with  the  nature  of  the  reaction 
and  embraced  both  chemical  and  physical  determinations. 

The  distribution  of  a  base  between  two  acids,  or  vice  versa, 
has  also  been  studied  from  this  standpoint  by  Julius  Thomsen 
(thermo-chemically,  1854),  Ostwald  (dilatometrically  and  by 
change  of  refractive  power,  1878),  Jellet  (optical  activity,  1875), 
and  Lellman  and  Schlesmann  (absorption  spectra,  1892). 

On  the  other  hand,  the  study  of  the  rate  of  chemical  change 
by  means  of  the  law  of  mass-action  (chemical  kinetics)  has 
resulted  in  the  classification  of  reactions  according  to  the  num- 
ber of  molecules  taking  part,  each  class  possessing  a  character- 
istic reaction  constant.  The  first  instance  of  this  was  the 
inversion  of  cane-sugar,  studied  polarimetrically  by  Wilhelmy  in 
1850,  and  more  recently  by  Ostwald  and  Arrhenius.  Ostwald 
(1883)  has  examined  many  other  cases  of  salt  or  ester  hydroly- 
sis and  his  work  has  been  supplemented  by,  that  of  Walker 
(1889)  and  Lowenherz  (1894)  who  showed  that  the  rate  of 
ester  hydrolysis  was  affected  by  the  acid,  but  not  by  the 
alcohol,  set  free  in  the  reaction.  All  of  this  tended  to  the 
view  that  the  determining  factor  of  the  hydrolysis  was  the 
hydrogen  ion,  an  idea  further  supported  by  the  fact  that  all 
such  reactions  appeared  as  bi-molecular  changes. 

*  It  has  been  proved  incidentally  that  the  only  two  forms  of  sulphur 
vapour  are  S2  and  S8,  others,  such  as  S6,  S4,  being  simply  mixtures  of 
these  two. 
13 


194         A  SHORT  HISTORY  OF  CHEMISTRY 

We  will  give  here  a  few  instances  of  the  various  types  of 
reaction  studied  in  this  way,  the  majority  being  uni-  or 
bi-molecular :  a  large  number  were  collected  by  van  't  Hoff 
("  Etudes  de  dynamique  chemique,"  1884) : — 

Unimolecular — 

Potassium  permanganate  and  oxalic  acid  (in  large  excess) — Harcourt 
and  Esson,  1865. 

Decomposition  of  dibromsuccinic  acid — Van  't  Hoff,  1884. 

Decomposition  of  radium  emanation — Mme.  Curie,  1904. 
Bimolecular — 

Inversion  of  cane-sugar — Wilhelmy,_i85o. 

R  .  COOEt  +  NaOH  (action   of  OH  ion)— Van  't  Hoff,  1884 ;  Ost- 
wald,  1887. 

CH2C1 .  COONa  +  NaOH  =  CH2(OH)COONa  +  NaCl— Van't  Hoff, 
1884. 

C2H5I  +  AgNO3— Chiminello,  1896. 

Decomposition  of  polybasic  acids — Knoblauch,  1898. 
Tet 'molecular — 

2FeCl3  +  SnCl2  =  SnCl4  +  2FeCl2— Noyes,  1895. 
Quadrimolecular — 

HBr03  +  HBr  \  ^  w    Walker  and  W.  Jud- 

2H  +~Br  +  Br03=HBrO  +  HBrO2)  j     son'  l8g8- 
Quinquemolecular — 

2KI  +  2K3Fe(CN)6  ^  Donnan  and    ^    Rossignol) 


Fe(CN)6  +  I3  J 


2Fe  (CN)e  +  3I-  =2    Fe(CN)6  +  I3  J 

We  have  said  that  hydrolysis  has  been  shown  to  be  effected 
by  the  "  catalytic  "  action  of  ions,  but  catalysis  is  a  term  which, 
although  of  long  standing,  does  not  mean  much. 

Many  instances  of  chemical  change  which,  if  not  altogether 
suspended,  were  very  slack  in  the  absence  of  a  definite  assisting 
substance,  became  known  during  last  century.  Such  additional 
substances,  which  passed  through  the  reaction  apparently  un- 
changed, were  called  catalysts. 

Interesting  additions  to  the  knowledge  of  this  subject  were 
made  when  Dixon  and  Baker  (1884-6)  showed  that  many 
common  reactions  (union  of  hydrogen  and  oxygen  ;  hydrogen 


THE  HISTORY  OF  PHYSICAL  CHEMISTRY     195 

and  chlorine  ;  ammonia  and  hydrochloric  acid,  etc.)  did  not 
take  place  in  the  perfect  absence  of  moisture,  when  Bigelow 
observed  a  kind  of  inverse  catalysis  in  that  many  organic 
substances  retarded  the  oxidation  of  sodium  sulphite  by  oxygen 
(1898)  and  when  Hjelt  (1891)  and  Henry  (1892)  observed 
cases  of  "  auto-catalysis  "  (the  rate  of  decomposition  of  sub- 
stances increasing  abnormally  in  consequence  of  one  of  the 
products  of  decomposition  acting  as  catalyst).  Catalysis  is  at 
present  usually  defined  as  the  alteration  of  the  rate  of  chemical 
reaction  by  the  presence  of  an  independent  substance. 

§  12.  The  Phase  Rule — The  manner  in  which  the  com- 
ponents of  a  physical  system  can  co-exist,  and  the  transforma- 
tions which  such  a  system  will  undergo  as  the  number  of  its 
components,  or  their  physical  state,  or  extraneous  conditions, 
are  altered,  were  summed  up  by  Gibbs  (1874-8),  and  ex- 
pressed by  a  simple  equation  which  has  been  called  the 
" phase  rule".  In  accordance  with  the  rule  numerous  dia- 
grams of  different  systems  have  been  constructed,  by  means  of 
which  the  composition  of  such  a  system  under  given  conditions 
can  be  estimated.  A  very  prominent  worker  in  this  field  has 
been  Roozeboom,  who  has  studied  numerous  systems  from 
1 888  onwards,  such  as  the  equilibrium  between  water,  ice,  and 
steam,  between  water  and  sulphur  dioxide,  between  the  different 
hydrates  of  metallic  salts  such  as  ferric  chloride  or  sodium  sul- 
phate. Roozeboom  has  endeavoured  to  depict  the  phase  rule 
as  a  complete  mechanical  expression  of  chemical  reactions,  but 
van  't  Hoff  (1892)  and  Ostwald  (1897)  agree  that  this  is  press- 
ing its  utility  a  little  too  far  !  Nernst  has  expressed  the  general 
conception  of  the  equation  when  he  calls  it  a  "  scheme  into 
which  complete  heterogeneous  equilibrium  fits  ". 

The  sharp  change  of  physical  properties  which  denotes  the 
passage  from  one  phase  to  another  has  been  called  the  "  eu- 
tectic  point "  by  Guthrie  (1885),  but  van 't  Hoff  s  term  "  transition 
point "  is  of  more  frequent  use.  Guthrie's  work  was  concerned 
with  the  investigation  of  mixed  melting-points. 


196        A  SHORT  HISTORY  OF  CHEMISTRY 

Similarly,  Konowalow  studied  the  vapour-pressure  curves  of 
various  liquid  mixtures  in  1881,  and  found  that  three  different 
types  of  curves  existed  :  continuous,  with  a  maximum,  and  with 
a  minimum  point. 

Van  't  Hoff  (1884-92)  elaborated  various  other  means  for 
determining  the  transition-point,  such  as  the  dilatometer  method, 
observation  of  sudden  rise  or  fall  in  temperature,  and  study  of 
solubility  curves;  Stewart  (1907)  has  used  absorption-spectra, 
and  Dunstan  and  Thole  (1908)  viscosity. 

Other  interesting  examples  of  phase-rule  systems,  besides 
those  due  to  Roozeboom,  are  the  allotropic  forms  of  sulphur 
(Reicher,  1884),  double  salt  formation  (Reicher,  1887  ;  Van  't 
Hoff  and  Von  Deventer,  1887),  and  the  allotropic  forms  of  tin 
(white  (metallic)  and  grey  (non-metallic),  Cohen,  1899). 


CHAPTER  XI 
THE  PROGRESS  OF  EXPERIMENTAL  METHOD 

§  i .  Improvements  in  Chemical  Apparatus — The  con- 
ditions under  which  a  modern  chemist  works  are  (or  should 
be)  ideal,  when  compared  with  those  of  a  few  generations  ago. 
In  a  well-equipped  laboratory  he  has  a  generous  expanse  of 
working  space,  abundance  of  clean,  roomy  drawers  for  his 
apparatus  and  preparations,  and  water,  gas,  electricity,  and 
even  "  vacuum  "  laid  on  to  his  bench.  The  alchemists  and 
most  of  the  phlogistonists  were  "  apothecaries,"  and  pursued 
their  researches  as  best  they  could  in  the  back  room  behind  the 
shop,  aided  by  a  spirit-lamp  or  a  charcoal  fire,  some  home-made 
glass  flasks  and  bottles,  and  a  water  supply  from  the  communal 
pump.  It  is  true  that  the  wealthier  chemists  (e.g.  Cavendish 
or  Priestley)  fitted  up  better  arranged  laboratories  for  them- 
selves, and  not  a  few  of  the  others  managed  to  get  under  the 
patronage  of  aristocrats  overburdened  with  money,  but  the 
majority  of  the  old  pioneers  of  our  science  had  to  shift  for 
themselves,  and  thereby  very  possibly  made  readier  practical 
chemists  than  the  modern  student  who  cannot  blow  a  spherical 
distilling  bulb  for  love  or  money.  The  modern  research  labora- 
tory emanated  from  Germany,  and  Wohler's  at  Gottingen  (1830), 
and  Bunsen's  at  Marburg  (1840),  may  be  regarded  as  the  first 
buildings  erected  for  practical  instruction  on  modern  lines. 
Such  laboratories  have  spread  enormously,  of  course,  since 
then,  and  now,  in  addition  to  purely  academic  institutes,  the 

197 


198         A  SHORT  HISTORY  OF  CHEMISTRY 

foremost  technical  works  have  their  own  research  and  testing 
laboratories,  supervised  by  chemists. 

Much  time  used  to  be  wasted  by  chemists  in  collecting 
material  as  a  basis  for  their  research,  but  this  is  obviated  nowaf- 
days,  since  several  firms  find  it  worth  their  while  to  devote 
themselves  to  the  manufacture  of  pure  chemicals  for  such 
purposes. 

With  reference  to  details  of  apparatus  the  following  summary 
will  show  how  comparatively  recent  is  the  introduction  of 
numerous  small  inventions  which  at  the  present  time  seem 
indispensable  : — 

Marggraf.  Use  of  microscope  for  crystals,  flame  tests  for  sodium  and 
potassium. 

Bergman.     Use  of  blowpipe  in  mineral  analysis. 

Berzelius.  Perfected  the  use  of  the  blowpipe  (inner  and  outer  flames,  with 
borax,  cobalt,  etc.)  ;  introduced  rubber  tubing,  water 
baths,  etc. 

Liebig.  Introduced  the  usual  glass  water-jacketed  condenser  first 
used  as  a  "  reflex  "  by  Kolbe  and  Frankland. 

Bunsen.  Introduced  the  Bunsen  gas  burner,  thermo  regulators,  con- 
stant level  water-baths,  water  suction  pumps,  systematic 
use  of  spectroscope,  etc. 

Beckmann.    Delicate  thermometers,  etc. 

Anschiitz.     Performed  the  first  distillation  under  reduced  pressure. 

Crafts.  Distillation  in  the  vacuum  of  the  cathode  light. 

§  2.  Improvements  in  Chemical  Methods — Dioscorides 
(about  100  A.D.)  used  to  prepare  quicksilver  from  cinnabar  by 
distillation,  and  methods  of  distilling  were  improved  by  the 
alchemists,  who  could  purify  alcohol  and  ether,  and  the  phlo- 
gistonists,  who  were  thereby  able  to  prepare  various  essential 
oils  and  esters. 

Reactions  of  double  decomposition  were  also  known  to  the 
ancients  and  alchemists,  as  evidenced  by  the  preparation  of 
caustic  alkalies,  of  ammonium  carbonate  (from  potashes  and 
sal  ammoniac),  and  of  silver  chloride  (from  rock  salt  and  lunar 
caustic).  Basil  Valentine  separated  different  metals  as  insol- 


PROGRESS  OF  EXPERIMENTAL  METHOD      199 

uble  salts,  and,  to  give  a  modern  instance,  Scheele  used  lime 
or  litharge  to  precipitate  most  of  his  organic  acids  from  the 
plant-juices  in  which  he  found  them. 

The  formation  of  hydrocarbons  by  reduction  has  already 
received  notice  (chap.  vii.  p.  1 1 8) ;  other  reduction  processes 
have  involved  the  use  of  hydrogen  sulphide  (in  acid  or  alkaline 
solution,  Zinin,  1842),  hydriodic  acid,  without  (Berthelot,  1867) 
or  with  phosphorus  (Baeyer,  1870),  sodium  in  the  form  of  wire 
(Hofmann,  1874),  of  ethylate  (Baeyer,  1879),  of  amylate  (Bam- 
berger,  1887)  or  of  amalgam  (Lippmann,  1865  ;  Baeyer,  1892), 
iron  filings  (Be*champ,  1854),  zinc  in  acid  (Girard,  1856), 
neutral  Lorin,  1866)  or  alkaline  solution  (Zogoumenny, 
1876),  tin  (Beilstein,  1864),  and  stannous  chloride  (Bottger 
and  Petersen,  1871). 

Of  oxidizing  agents,  in  addition  to  the  previously-mentioned 
ozone  and  hydrogen  peroxide,  potassium  permanganate  and 
nitric  acid  (Debus,  1858)  have  always  been  favourites  with 
organic  chemists.  Other  interesting  applications  have  been 
made  of  chromic  acid  (potassium  salt,  Penny,  1852  ;  the  acid 
itself,  Graebe,  1880),  soda  lime  (first  made  and  used  in  this 
connexion  by  Dumas  and  Stas,  1840),  bromine  (for  sugars, 
Blomstrand,  1862  ;  E.  Fischer,  1889),  alkaline  silver  oxide 
(Tollens,  1882),  and  sulphuric  acid  (for  mercaptans,  Erlen- 
meyer,  1861  ;  conversion  of  piperidine  to  pyridine,  Ko'nigs, 
1879). 

Substitution  processes  having  played  such  an  important  role 
in  organic  chemistry,  we  will  tabulate  the  chief  methods  which 
have  been  utilized  in  this  connexion : — 

Nitration — 

HNO3  +  H2SO4— Schonbein,    1846;    modified    by    Martius,    1868; 
Nolting,  1884  ;  Nietzki,  1887 ;  and  others. 

HNO3  +  CH3 .  COOH— Cosak,  1880. 

Oxidation  of  nitroso-compound — Schraube,  1875. 

AgNOa  (for  fatty  compounds) — V.  Meyer,  1874. 
Methylation — 

Dimethyl  sulphate — Badische  Anilin-Soda  Fabrik. 


200          A  SHORT  HISTORY  OF  CHEMISTRY 

Bromination — 

Bromine  in  chloroform,  carbon  disulphide  (Michael,  1866),  or  acetic 

acid  (Graebe  and  Weltner,  1891). 
Chlorination — 

C12  gas—"  The  four  Dutch  chemists,"  1795. 

C12  liquid — Badische  Anilin-Soda  Fabrik,  1890. 

Diazochlorides — Griess,  1885. 

Cu2Cl2  and  diazo-bodies — Sandmeyer,  1884. 

Reduced  copper  and  diazo-bodies — Gattermann,  1890. 

PC15— Dumas  and  Pdligot,  1836. 

POC13— Chiozza,  1853. 

PC13— Be-champ,  1856. 

SOC12— Heumann,  1883. 
lodination — 

Iodine  in  carbon  disulphide  (Schwald,  1883)  or  aqueous  potassium 

iodide  (Baeyer,  1885).     (Application  limited.) 
Halogen  Carriers — 

Iodine  (for  C12  and  Br2)— Miiller,  1862 ;  Kekule,  1866. 

Various  metal  chlorides — Perkin  and  Duppa,  1859  ;  L.  Meyer,  1875  ; 
Beilstein,  1876;  Gustavson,  1881. 

Phosphorus  (for  Br2  and  I2) — Serullas,  1848  ;  Personne,  1861. 
Fluorination — 

Various  methods — Reinsch,  1840;  Fremy,  1854;  Borodine,  1862. 
Sulphonation — 

(NH4)2SO3— Piria,  1850  (for  nitro-bodies). 

Fuming  H2SO4— Barth,  1868  (with  P2O5,  1871). 

100  per  cent.  H2SO4 — Lunge,  1889. 

K2S2O7 — E.  Fischer,  1877  (for  phenylhydrazine  derivatives). 
Addition  of  bisulphite — Bertagnini,  1853  (aldehydes)  ;  Messel,  1871. 

Cl .  SO3H— Limpricht,  1885. 
Sulphination — 

Cu  powder,  SO2  and  diazo-compounds— Gattermann,  1899. 

S02,  A1C13  and  aromatic  derivatives — Smiles  and  Le  Rossignol,  1908. 

Finally,  we  must  refer  to  hydrolysis  or  molecular  fission, 
effected  by  aqueous  or  alcoholic  alkalies,  baryta  (Baeyer,  1881), 
silver  oxide  (Hantzsch,  1886),  but  not  ammonia,  on  account 
of  secondary  reactions  (Liebig,  1834).  Sulphuric  or  hydro- 
chloric acids  (Lautemann,  1863;  Gal,  1865)  have  also  been 
used  as  saponifiers,  while  for  more  profound  decomposition 
recourse  has  often  been  had  to  aluminium  chloride  (Hartmann 


PROGRESS  OF  EXPERIMENTAL  METHOD     20! 

and  Gattermann,  1892,  for  phenol  ethers),  hydriodic  acid 
(Zeisel,  1885,  for  the  same),  or  fusion  with  caustic  alkali  for 
alkaloids,  etc.  (Pelletier,  Laurent,  and  others);  Kolbe,  1860 
(salicylic  acid  synthesis)  ;  Weselsky  and  Benedikt,  1878,  re- 
duction of  nitro-  to  azo-phenols;  a  suitable  apparatus  for 
potash  fusions  was  designed  by  Liebermann,  1888. 

§  3.  Development  of  Analytical  Methods — Basil  Valen- 
tine separated  a  few  metals  by  precipitation  with  suitable  acids 
or  bases,  and  thus  recognized  alloys  containing  copper,  iron, 
silver,  and  gold.  Later  on  Tachenius  was  able  to  give  a 
partial  scheme  for  separating  mineral  substances,  using  pre- 
cipitation reactions,  and  depending  largely  on  the  colours  of 
the  precipitates.  The  word  analysis  was  first  used  to  describe 
such  processes  by  Boyle,  and  he,  as  well  as  his  successors, 
Hofmann,  Marggraf,  Scheele,  and  others,  devised  numerous 
other  isolated  tests  for  metals  and  acids,  and  mineral  earths. 

(a)  Inorganic  Qualitative. — The  scattered  reactions  known 
towards  the  close  of  the  phlogistic  era  were  collected  by  Berg- 
mann,  who  also  arranged  a  systematic  series  of  reagents  for 
testing,  and  who,  with  Cronstedt  and  others,  was  instrumental 
in  introducing  the  mouth  blowpipe  into  analytical  operations. 
Berzelius  and  Klaproth  did  much  for  this  branch  of  chemistry, 
the  extent  of  which  in  1801   may  be  gathered  from  the  hand- 
books of  mineral  analysis  published  at  that  date  by  Lampadius 
and  others.     Berzelius  moreover  introduced  the  modern  division 
of  metals  and  acids  into  groups,  a  work  which  has  been  carried 
on  throughout  the  last  century,  notably  by  Rose,  Fresenius,  and 
Noyes.     The  separation  of  closely  allied  metals,  such  as  the 
rare  earths,  by  means  of  fractional  crystallization  of  their  sul- 
phates, nitrates,  oxalates,  chromates,  bromates  (James,  1907), 
or  acetylacetone  derivatives  (Urbain,  1896)  also  deserve  men- 
tion here,  and  so  does  the  general  analytical  work  of  Fenton, 
1895-. 

(b)  Inorganic  Quantitative. — The  estimation  of  a  substance  in 
compound  rather  than   element  form  was  first  advocated  by 


$02         A  SttOkT  HISTORY  OF  CHEMISTRY 

Bergmann,  who  weighed  calcium  as  oxalate,  sulphuric  acid  as 
barium  salt,  lead  as  sulphide,  etc.  Previous  to  this  Marggraf 
had  used  silver  chloride  to  determine  silver  in  alloys,  and 
Black  had  shown  how  to  estimate  magnesia  as  carbonate.  The 
quantitative  analysis  of  minerals  received  attention  from  Klap- 
roth  and  from  Bergmann,  who  decomposed  silicates  by  alkaline 
fusion,  but  it  was  Berzelius  who  made  the  greatest  advances 
here,  using  much  smaller  amounts  of  his  substances  than 
previous  workers,  and  so  facilitating  manipulation.  He  taught 
the  modern  methods  of  filtering  through  thin  bibulous  paper, 
and  of  subsequent  incineration  of  the  filter  and  ash  determina- 
tion. He  also  introduced  new  methods  for  breaking  up  miner- 
als, such  as  oxidation  by  nascent  chlorine  and  evaporation  with 
strong  hydrochloric  acid.  New  methods  of  inorganic  quanti- 
tative work,  as  well  as  improvements  in  those  existing,  have 
been  due  more  especially  to  Wohler,  Rose,  and  Fresenius.  Of 
late  electro-chemical  methods  have  become  prominent ;  these 
were  introduced  by  Classen,  and  made  more  practicable  by 
the  use  of  rotating  electrodes  (Gooch  and  F.  Moll  wo  Perkin). 
Sand  (1907)  has  recently  perfected  the  rapid  separation  of 
antimony  from  tin  and  of  other  metallic  mixtures  difficult  to 
manipulate  gravimetricaHy.  We  should  also  notice  the  recent 
use  of  silica  crucibles  and  combustion  tubes,  superior  to  glass 
or  porcelain  in  that  they  readily  withstand  sudden  temperature 
changes,  and  of  the  crucibles  devised  by  Gooch  for  rapid  quan- 
titative work,  in  which  the  use  and  subsequent  drying  and 
incineration  of  a  filter-paper  is  avoided. 

(c)  Organic  Qualitative. — Although  in  the  process  of  burning 
an  organic  substance,  van  Helmont  and  Boyle  noticed  the 
formation  of  water,  and  Priestley  detected  carbonic  acid  gas,  and 
Scheele  observed  both,  yet  it  was  left  to  Lavoisier  to  state  de- 
finitely, after  the  erection  of  his  oxygen  theory,  that  carbon  and 
hydrogen  occurred  in  all  organic  bodies  together,  sometimes 
with  oxygen  and  nitrogen.  The  presence  of  the  latter  element 
was  detected  by  Berthollet  by  conversion  to  ammonia,  and  by 


PROGRESS  OF  EXPERIMENTAL  METHOD      263 

Lassaigne  (1843)  by  tne  formation  of  sodium  cyanide  on  fusion 
with  sodium.  Halogens  were  also  detected  by  this  means, 
while  Berzelius  usually  tested  for  phosphorus  and  sulphur  by 
oxidation  with  nitric  acid  to  phosphoric  or  sulphuric  acids. 
Beyond  such  elemental  testing,  there  is  little  to  be  recorded 
here  of  qualitative  organic  analysis.  As  new  classes  of  com- 
pounds were  discovered  and  new  radicles  became  known, 
methods  of  identifying  the  different  groups  naturally  followed 
from  a  knowledge  of  their  behaviour  and  nature, 

(d)  Organic  Quantitative. — Lavoisier  used  to  determine  the 
amount  of  carbon  and  hydrogen  in  organic  substances  by  heating 
them  in  oxygen  or  with  mercury  or  lead  oxides,  and  catching 
the  products  of  combustion  in  suitable  absorbents  (he  is  said  to 
have  used  blotting-paper  to  absorb  the  water  formed !).  Saussure 
and  Thenard  (1807)  used  potassium  chlorate  as  oxidant,  but 
were  met  with  the  difficulty  of  the  violent  action  which  thus  en- 
sued. Berzelius  tried  to  modify  this  by  adding  common  salt  as 
a  diluent,  Gay-Lussac  introduced  the  use  of  copper  oxide  in  1815 
and  finally  Liebig  about  1830  devised  the  combustion-furnace 
practically  as  we  know  it  to-day.  With  reference  to  the  collection 
of  the  products,  Berzelius  improved  on  Lavoisier's  method  for  the 
water  by  substituting  calcium  chloride  for  the  blotting-paper, 
and  much  more  recently  Mathesius  commenced  to  use  pumice 
soaked  in  strong  sulphuric  acid  (1882),  the  most  convenient 
form  of  apparatus  being  that  devised  by  Collie  (1895).  The 
carbon  dioxide  has  always  been  collected  in  caustic  potash, 
different  kinds  of  absorption  bulbs  having  been  invented  by 
Liebig  (1843),  Geissler  (1880),  and  Delisle  (1891)  amongst 
others.  Other  methods  of  oxidizing  the  carbon  have  been  used 
by  Kapfer  (vapour  and  oxygen  passed  over  spongy  platinum, 
1876),  by  Messinger  (oxidation  in  the  wet  way  by  chromic  acid, 
1888),  and  by  Dennstedt,  who  has  recently  perfected  a  furnace 
for  rapid  analyses  of  organic  compounds. 

Nitrogen  has  been  determined  as  gas  by  the  combustion 
method  of  Dumas  (1830),  as  ammonia  by  Will  and  Varrentrapp 


A  SHORT  HISTORY  OF  CHEMISTRY 

(heating  with  soda-lime,  1841)  and  by  Kjeldahl  (heating  with 
sulphuric  acid,  1883) ;  the  last  method  has  proved  very  service- 
able for  rapid  technical  analyses. 

Halogens  have  been  estimated  by  conversion  to  metal  halide, 
either  by  heating  the  substance  with  lime  (Piria  and  Schiff,  1879) 
or  by  heating  under  pressure  with  fuming  nitric  acid  (Carius, 
1860),  and  similarly  sulphur  and  phosphorus  can  be  converted 
to  sulphuric  or  phosphoric  acids  by  fusion  with  caustic  potash 
and  nitre  (Liebig,  1849)  or  by  the  Carius  method.  The  fusion 
of  organic  substances  with  sodium  peroxide  must  also  be  men- 
tioned as  a  means  of  estimating  either  of  these  last  elements 
(Edinger,  1895). 

We  must  refer,  too,  to  a  variety  of  methods  introduced  at 
different  periods  for  the  estimation  of  particular  compounds 
or  radicles : — 

Alcohol.     Specific  gravity  (Reaumur,  1733 ;    Brisson,    1768).      Re- 

fractometer. 

Sugar.  Polarimeter  (Clerget,  1870) ;  also  recently  by  refractometer. 
Methoxyl,  — OCH3)  Heating  with  hydriodic  acid  and  weighing  asAgl. 
Ethoxyl,  — OC2H5  /Zeisel,  1885 ;  Perkin  improved  apparatus,  1904. 

Nitro N0a    }  Reduction  by  tin  and  volumetric  estimation  of  unused 

Nitroso-  — NOJ      metal  (Limpricht,  1878). 
Phenols  and  some  other  hydroxylic  compounds — 

(i)  Formation  of   benzoyl   derivative   and   hydrolysis   (Schotten, 

Baumann,  1887). 
(ii)  Hydrolysis  of  acetyl  derivative,  formed  by  heating  with  acetic 

anhydride  and  sodium  acetate  (Liebermann,  1874). 
Carboxyl  group — 

(i)  By  formation  of  bisulphite  compound  (Bertagnini,  1853). 
(ii)  By  formation  of  phenylhydrazone  (E.  Fischer,  1877),  or  semi 

carbazide  (Baeyer,  1894). 
Amino  group — 

(i)  Action  of  nitrous  acid  and  measurement  of  evolved  N2  (Heintz, 

1866). 
(ii)  Analysis  of  salts  or  acetyl  or  benzoyl  compounds. 

(e)  Volumetric  Analysis. — The  founder  of  this  very  useful 
means  of  analysis  was  Gay-Lussac  who,  from  1824-32,  de- 


PROGRESS  OF  EXPERIMENTAL  METHOD     205 

vised  titration  methods  for  the  estimation  of  acids  and  bases 
(alkalimetry),  of  bleaching-powder,  of  chlorine,  and  of  silver 
(chlorimetry),  the  latter  depending  on  the  reaction  between  a 
chloride  and  a  soluble  silver  salt.  Volhard  (1874)  devised  the 
sulphocyanide  method  of  silver  titration,  Marguerritte  (1846) 
the  permanganate  method  for  iron  estimation,  and  Bunsen  (1853) 
the  determination  of  iodine  by  sodium  bi-sulphite.  Improved 
forms  of  the  necessary  apparatus  (burettes,  pipettes,  etc.)  were 
brought  forward,  notably  by  Bunsen  and  by  Mohr ;  and,  within 
the  past  fifty  years,  modifications  of  the  above  half-dozen  funda- 
mental methods,  too  numerous  for  individual  attention,  have  been 
arranged  by  a  multitude  of  chemists  so  that,  at  the  present  day, 
there  is  hardly  an  element  or  a  compound,  inorganic  or  organic, 
which  cannot  directly  or  indirectly  be  brought  within  their  scope. 

Reference  may  be  suitably  made  here  to  the  work  on  the 
theory  of  "indicators"  (i.e.  the  class  of  substances  used  in 
alkalimetry  to  show  by  their  colour  if  the  reaction-mixture  is 
acid  or  alkaline),  done  more  especially  by  Hantzsch,  A.  G.  Green, 
A.  G.  Perkin,  Hewitt,  and  Veley. 

(/)  Gas-analysis. — During  the  phlogistic  period  the  qualita- 
tive separation  of  a  few  gases  became  known ;  thus  caustic 
potash  was  used  to  absorb  carbon  dioxide  and  nitrogen  peroxide, 
and  moist  ferrous  hydroxide  or  phosphorus  to  remove  oxygen. 
Schemes  for  systematically  detecting  various  gases  were,  how- 
ever, first  brought  out  by  Priestley,  Lavoisier,  Dalton,  and 
Gay-Lussac.  The  qualitative  side  of  the  question  was  first 
studied  by  Cavendish,  who  used  to  employ  explosion  methods 
(eudiometry  ;  hydrogen  and  air  ;  nitrogen  and  oxygen ;  hydrogen 
and  chlorine,  etc.).  Important  work,  leading  up  to  the  modern 
methods,  was  carried  out  by  Henry,  by  Gay-Lussac  and  by 
Bunsen ;  and  finally,  the  possibility  of  determining  the  com- 
position of  a  gaseous  mixture  by  successive  removal  of  its 
constituents  by  suitable  absorbents  was  realized  by  the  gas 
burettes  and  absorptiometers  of  Winkler,  Hempel,  and  Lunge 
1875-90). 


206         A  SHORT  HISTORY  OF  CHEMISTRY 

§  4.  The  Determination  of  Atomic  Weights— Reference 

has  been  made  at  different  points  in  previous  chapters  to  ad- 
vances in  atomic  weight  determination,  such  as  the  application 
of  Dulong  and  Petit's  law  of  constant  specific  atomic  heat,  of 
Mitscherlich's  discovery  of  isomorphism,  the  more  recent  use 
of  gas-densities  corrected  by  van  de  Waal's  constants,  and 
Cannizzaro's  rules  for  selecting  the  correct  multiple  of  the 
chemical  equivalent. 

It  is  therefore  intended  to  give  here  only  a  resume  of  the 
accurate  measurement  of  chemical  equivalents. 

Dalton  based  the  atomic  theory  on  relatively  few  and  in- 
accurate practical  data,  and  we  are  indebted  to  Berzelius  for 
the  greater  number  of  satisfactory  values  of  the  equivalents  of 
the  elements  then  known.  Some  of  the  methods  he  used  are 
quoted  below,  and  some  idea  of  the  indefatigable  nature  of  his 
work  will  be  gathered  when  it  is  remembered  that  in  a  decade 
he  made  careful  analyses  of  over  two  thousand  compounds. 

Another  notable  analyst  was  Dumas  who,  after  finding  dis- 
crepancies between  Berzelius'  numbers  and  his  own  (obtained 
from  vapour  density),  and  also  detecting  an  error  in  the  Berzelian 
value  for  carbon,  applied  himself  in  succeeding  years  to  several 
equivalent  determinations,  using  especially  the  precipitation  of 
halides  of  the  element  by  silver  nitrate.  More  systematic  study 
of  the  subject  was  entered  upon  by  Marignac  (1842-58)  and 
Stas  (1840-65),  the  precautions  against  error  taken  by  the 
latter  being  so  elaborate  that  for  nearly  forty  years  no  one 
cared  to  question  his  experimental  accuracy ;  these  investiga- 
tions aimed  at  securing  a  series  of  independent  values  for  each 
element,  based  upon  the  numbers  (exceedingly  carefully  obtained) 
for  two  or  more  of  the  following :  sodium,  potassium,  silver, 
chlorine,  bromine,  iodine. 

The  more  recent  use  of  the  gas  constants,  however,  has  led 
in  the  hands  of  Leduc  (1895),  Guye  (1902),  Gray  (1905),  and 
others  to  the  detection  of  small  but  very  perceptible  errors  in 
some  of  Stas'  fundamental  values,  and  in  consequence  of  this 


PROGRESS  OF  EXPERIMENTAL  METHOD     207 

the  redetermination  of  atomic  weights  has  been  attended  to, 
both  by  density  methods  (Gray,  1905-;  Guye,  1905-,  etc.) 
and  by  chemical  methods,  in  which  an  American  school  of 
chemists,  under  Clarke  and  Richards,  has  of  late  years  been 
very  prominent. 

Our  summary  would  not  be  complete  without  reference  to 
the  method  by  which  the  general  selection  of  the  most  reliable 
values  is  made,  namely,  by  means  of  an  annual  international 
commission  of  four  distinguished  workers,  French,  German, 
American  and  English. 

We  will  conclude  with  a  few  instances  of  the  chief  methods 
of  gravimetric  equivalent  determination  which  have  proved 
serviceable : — 

Precipitation    of    halide    by    Ba,  Sr,  1858,  Marignac ;  As,  Sb,  Sn,  Pb, 
silver  nitrate  1856-9,    Dumas  ;     Li,    1860,    Stas ; 

Al,  1880,  Mallet ;  Ti,  1885,  Thorpe. 

Conversion    of    sulphate    to    Al,  1812,  Berzelius ;  Be,  Th,  1880-2,  Nil- 
oxide  son ;  Cr,  Cu,  Zn,  1884,  Baubigny. 
Conversion  of  oxide  to  sul-     Mn,  1883,  Marignac ;  Sc,  1880,  Nilson. 

phate 

Conversion  of  chlorate,  etc.,     Cl,  Br,  I,   1842-6,    Marignac  and  Stas; 
to  halide  by  heat  K,   1842-6,   Marignac  ;    Ag,   1860-5, 

Stas. 

Conversion    of    element    to    C,  1882,   Roscoe ;  11885,  van  der   Plaats; 
oxide  P,   1885,  van  der   Plaats  ;  In,    1867, 

Winkler. 
Reduction  of  oxide  to  element    Fe,  1844,  Erdmann  and  Marchand;    Mo 

1859,  Dumas.      , 

Ignition     of     salts,    leaving    Au,  1887,  Thorpe  and  Lawrie;  S  (from 
element  silver  sulphate),  1860-5,  Stas ;  Pb,  Ir 

Os  1878-88,  Seubert. 

Volume    of    hydrogen    from    Zn,  1884,  Ramsay  and  Reynolds, 
metal  and  acid 

Numerous  other  devices  have  naturally  been  used,  but  the 
above  are  the  most  interesting. 

We  may  remark  upon  the  especially  careful  determinations 
made  in  the  case  of  argon  and  potassium,  iron,  cobalt,  and 


208         A  SHORT  HISTORY  OF  CHEMISTRY 

nickel,  and  iodine  and  tellurium,  owing  to  anomalies  occurring 
in  the  periodic  system  under  the  present  atomic  weight  values. 
In  no  case  has  the  discrepancy  been  removed ;  in  the  last  in- 
stance, many  efforts  have  been  made  to  ascertain  whether 
tellurium  is  a  mixture  of  elements,  but  the  most  recent  and 
exhaustive  work  of  Baker  and  of  Marckwald  (1907)  dis- 
countenances this  view. 


APPENDIX  A 

BIOGRAPHICAL  INDEX  OF  CHEMISTS 

IN  the  following  pages  the  scope  of  the  work  and  a  few 
other  points  of  interest  about  the  lives  of  some  150  typical 
chemists  are  briefly  and  it  is  hoped  concisely  summarized. 
The  names  are  given,  as  far  as  possible,  chronologically  and  in 
the  order  of  the  six  chemical  periods  (chap.  i.  p.  4).  It  is 
to  be  understood  that  neither  the  workers  chosen  nor  the  ac- 
counts of  their  work  offer  in  the  slightest  degree  a  complete 
compilation  of  even  the  leading  men  of  our  science ;  but  pos- 
sibly a  clearer  idea  of  individual  contributions  to  chemistry 
will  be  gained  by  a  perusal  of  this  appendix. 

ALCHEMICAL  PERIOD 

Geber  (end  of  eighth  century),  Arab  physician  and  first  noted 
alchemist.  Wrote  several  books,  which  show  his  know- 
ledge of  the  common  metals,  salts,  acids,  and  alkalies,  their 
preparation  and  purification  (crystallization,  distillation, 
filtration,  sublimation),  and  his  beliefs  in  transmutation 
and  in  mercury  and  sulphur  as  the  two*  primal  elements. 

Paracelsus  (1493-1541).  A  Swiss  iatrochemist  of  great  ability, 
obscured  by  conceit  and  fiery  temperament.  Initiated 
many  reforms  in  medicine  and  chemistry.  Introduced 
alcohol  preparations,  lead,  and  antimony  compounds,  and 
"  vitriols  "  as  remedies.  Improved  practical  metallurgical 
methods. 

Van  Helmont  (1577-1644),  Brussels  chemist  of  great  percep- 
tion. Realized  that  "  fire  "  is  not  material ;  the  "  con- 
servation of  matter  "  in  isolated  instances  ;  differentiated 
the  more  common  gases,  especially  "  gas  sylvestre  "  (CO2) ; 
14  209 


210         A  SHORT  HISTORY  OF  CHEMISTRY 

and  created  "  physiological  chemistry  "  by  insisting  on  the 
study  and  importance  of  the  reactions  and  secretions  of  the 
body. 

-  Boyle,  Robert  (1626-91),  Irishman.  Studied  in  France,  Geneva, 
Italy,  Oxford  (1654-68),  and  London  (President  of  the 
Royal  Society,  1680-91).  Unbiassed,  truly  scientific  char- 
acter. Wrote  several  brilliant  books.  Denned  "  element," 
"  compound,"  "mixture,"  "analysis,"  predicted  the  exist- 
ence of  many  more  elements  than  were  then  recognized, 
and  advanced  a  "  corpuscular  "  theory  of  matter.  Inves- 
tigated the  relation  of  pressure  to  volume  in  a  gas,  the 
manufacture  of  various  alloys,  glass,  and  phosphorus,  dis- 
covered methyl  alcohol  (wood-spirit),  phosphoric  acid, 
darkening  of  silver  salts  by  light,  improved  analytical 
tests,  etc.  etc. 

Kunkel,  Johann  (1630-1702),  German  Court  alchemist.  Be- 
lieved in  transmutation,  but  relentlessly  denounced  the 
charlatans.  Improved  the  manufacture  of  various  iron 
and  copper  alloys,  glass,  phosphorus,  etc. 

\/JBecher,  Johann  (1635-82).  Revived  Geber's  three  principles 
as  "  terrae  mercurialis,  vitra  and  pinguis  ".  The  last  gave 
rise  to  Stahl's  theory  of  phlogiston. 

PHLOGISTIC  PERIOD 

aw,  John  (1645-79),  physician.  Recognized  (1669)  that 
the  "  spiritus  nitro-aereus  "  present  in  both  air  and  nitre 
unites  with  metals  on  calcination. 

G.  E.  (1660-1734),  Prussian  court  physician.  Trained 
a  number  of  eminent  chemists,  and  devised  his  phlogiston 
theory  to  explain  oxidation  and  reduction  processes. 
*-  ^Hoffmann,  Friedrich  (1660-1742),  Prussian  professor.  Views 
similar  to  Stahl's  on  combustion,  but  resembling  others  on 
calcination.  Developed  qualitative  analysis,  and  investi- 
gated many  mineral  waters. 

<Rouelle>    G.   F.    (1703-70).      Taught   Lavoisier   and    Proust. 

Defined  neutral,  acidic,  and  basic  salts  (1744);  discovered 

urea  (1737),  sulphuretted  hydrogen  and  other  compounds. 

Marggraf,    A.    S.    (1709-82),    pupil    of    Stahl  and   German 

professor.      Noted   increase   in   weight  on   oxidation   of 


APPENDIX  A  211 

phosphorus;  discovered  beet-sugar  (1747),  alumina  (as 
distinct  from  lime,  1754),  and  introduced  the  microscope 
into  analysis ;  estimated  silver  as  chloride  and  knew  the 
flame  tests  for  the  alkalies. 

"  Black,  Joseph  (1728-99),  Scottish  professor.  Worked  at  latent 
heat  (1762),  specific  heat,  thermometry,  calorimetry,  and 
elucidated  nature  of  CaO,  MgO,  NaOH  and  their  car- 
bonates. Supported  Lavoisier's  oxygen  theory  in  preference 
to  that  of  phlogiston. 

*"£ergtnann,  T.  (1735-84),  Swedish  professor.  Important  for 
his  views  on  chemical  affinity  (1777),  development  of 
mineral  analysis  (blowpipe,  systematic  tests,  gravimetric 
methods  for  Ca,  H2SO4,  Pb,  etc.),  discovery  of  molyb- 
denum and  tungsten,  1778,  and  theory  of  "vital  force" 
for  organic  compounds. 

Scheele,  C.  W.  (1742-86),  Swedish  apothecary.  Pioneer  in 
nearly  every  branch  of  chemistry,  with  great  power  of 
observation.  Discovered,  amongst  other  substances, 
oxygen  (1774),  chlorine,  manganese  (1778),  barium  (dis- 
tinct from  lime),  phosphoric  acid  in  bones,  fluorine,  hydro- 
gen persulphide,  arsine  ;  and  in  organic  chemistry,  glycerol 
(1779),  aldehyde  (1774),  and  tartaric  (1769),  uric  and 
oxalic  (1776),  lactic  and  pyromucic  (i78o),prussic  (1782), 
malic  (1785),  pyrogallic  (1786),  and  citric  acids  ;  improved 
qualitative  analysis,  developed  actinic  and  pneumatic 
chemistry,  etc.  A  confirmed  phlogistonist. 

Priestley ',  Joseph  (1733-1804),  theologian  and  chemist. 
Staunch  upholder  of  the  phlogistic  theory.  Lived  at 
Birmingham  and  subsequently  died  in  America.  Im- 
mensely enriched  pneumatic  chemistry  ; '  used  mercury  for 
collecting  gases,  invented  the  pneumatic  trough ;  discovered 
ammonia  gas,  nitrous  and  nitric  oxides,  oxygen  (1774); 
isolated  SO2 ;  showed  that  burning  organic  bodies  pro- 
duced carbonic  acid ;  regarded  hydrogen  as  "  phlogiston  ". 

Richter,  J,  B.  (i 762-1807).  Invented  the  term  "  stoichiometry," 
and  exactly  determined  the  equivalents  of  various  com- 
pounds, especially  in  reactions  of  "  double  decomposi- 
tion ".  Obscured  the  value  of  his  results  by  expressing 
them  phlogistically. 

Cavendish^    Henry    (1731-1810),    English   philosopher.     In- 


2i2         A  SHORT  HISTORY  OF  CHEMISTRY 

vented  eudiometry  and  studied  the  volumetric  composition 
of  water,  nitric  acid,  air,  etc.  Discovered  hydrogen 
(1773)  >  estimated  the  density  and  weight  of  the  earth  ; 
like  Priestley  and  Scheele,  in  spite  of  his  own  anti-phlogistic 
work,  he  always  subscribed  to  the  phlogistic  theory. 

MODERN  (FUNDAMENTAL)  PERIOD 

Lavoisier,  Antoine  (1743-1794),  mathematician,  physicist,  and 
chemist.  Great  politician  ;  "  Fermier- General  ".  Mur- 
dered by  the  French  Revolutionary  Court.  Insisted  on 
accurate  measurements  and  attention  to  the  weights  of 
reacting  substances.  Showed  that  metal  "  calces  "  were 
heavier  than  the  metals  producing  them  (1772);  proved 
the  "  conservation  of  matter  "  (1774)  ;  investigated  oxida- 
tion of  P,  S  (i772),\Sn  (1774),  Hg,  etc.  (1775);  replaced 
"phlogiston"  by  "oxygen"  (1777);  systematized  the 
terms  acid,  base,  organic  compound,  salt,  etc.  Devised 
the  combustion  process  for  analyzing  organic  substances. 
Improved  gas-analysis  ;  gave  hydrogen  and  oxygen  their 
present  names;  quantitatively  synthesized  water  (1783); 
damaged  his  reputation  by  trying  to  rob  Priestley  and 
Cavendish  of  the  merit  of  their  respective  discoveries  of 
oxygen  and  the  compound  nature  of  water. 
- Morveau,  G.  de  (1733-1816),  Professor  at  Ecole  polytechnique, 
Paris,  and  friend  of  Lavoisier.  Introduced  the  first  syste- 
matic nomenclature  for  chemical  substances,  1782  ;  showed 
that  soda-crystals  could  be  made  from  Glauber's  salt  by 
heating  with  coke  and  iron. 

Berthollet,  C  L.  Count  (1748-1822),  Professor  in  Paris. 
Chemist  under  Napoleon  in  Italy  and  Egypt.  Renounced 
the  phlogiston  theory  in  1785;  investigated  ammonia, 
prussic  acid,  sulphuretted  hydrogen,  and  chlorine  ("  oxy- 
muriatic  gas ") ;  used  sodium  hypochlorite  solution  as 
bleaching  agent  ("Eau  de  Javelle,"  1800)  ;  believed  mass 
to  be  the  predominant  factor  in  chemical  change,  1801 ; 
controversy  with  Proust  on  the  law  of  multiple  propor- 
tions, 1801-7. 

'l 'Proust,  J.  L.  (1755-1826),  Parisian  apothecary  and  later  pro- 
fessor in  Spain.     Noted  for  his  work  just  mentioned,  in 


APPENDIX  A  213 

which  by  means  of  basic  copper  carbonates,  oxides  of  tin 
and  iron,  and  sulphides  of  iron,  he  established  the  law  of 
multiple  proportions.  Also  worked  at  organic  chemistry. 

' Fourcroy,  A.  F.  (1755-1800),  Professor  in  Paris.  Advanced 
animal  and  mineral  chemistry. 

(•Vauquelint  L.  N.  (1763-1829),  Professor  in  Paris.  Discovered 
various  elements  (Be,  and  Cr,  1797),  many  naturally- 
occurring  organic  compounds  (asparagine,  1805 ;  cam- 
phoric and  quinic  acids,  etc.),  and  cyanic  acid  (1818). 

i  W.  H.  (1766-1829),  English  physicist  and  chemist. 
Worked  at  emission  and  absorption  spectra  (1802),  dis- 
covered some  of  the  platinum  metals  (1803-4),  some 
organic  substances  (cystine),  and  regarded  Dalton's  atoms 
as  "equivalents"  only  (1814). 

i  M.  H,  (1743-1821),  first  Professor  of  chemistry  at 
Berlin.  Discovered  strontium  (1790),  zirconium,  tel- 
lurium (1798),  uranium  and  cerium  (1803),  composition 
of  honeystone  (aluminium  mellitate,  1799).  Improved 
mineral  analytical  methods  considerably. 
Dalton^John  (i  766-1844),  Teacher  at  Manchester.  Discovered 
colour-blindness  (1793),  composition  of  carbon  dioxide 
(1803),  and  olefiant  gas,  etc.,  law  of  partial  pressures 
(1807),  an<3  enunciated  his  atomic  theory  (1807-8);  in- 
vented a  system  of  elementary  symbols. 
Davy,  Sir  H.  (1778-1829),  English  chemist.  Worked  at 
nitrous  oxide  and  phosphorus  pentachloride  (1800)  ;  iso- 
lated electrolytically  the  metals  of  the  alkalies  (1807)  and 
alkaline  earths  (1808);  electro-chemical  theory,  1807; 
elementary  nature  of  chlorine  (1810);  chlorine  oxides, 
complex  acids,  miners'  safety-lamp,  chemistry  of  flame 
and  actinometry. 

Gav-Lussac,  J.  L.  (1778-1850),  Professor  at  Paris.  Taught  by 
Berthollet.  Worked  at  inorganic  chemistry  (halides  of 
nitrogen  and  phosphorus,  etc.,  1800) ;  gas  analysis  and 
physical  research  (1801-8) ;  law  of  volumes,  1808  ;  chlorine, 
1810;  introduced  copper  oxide  in  the  combustion  pro- 
cess, 1815  ;  complex  inorganic  acids,  1815-20;  cyanogen, 
1815-22;  invented  volumetric  analysis  (acid  and  alkali- 
metry, silver,  chlorine,  1824-32);  improved  manufacture 
of  oxalic  (1829)  and  sulphuric  acids  (1827). 


2i4         A  SHORT  HISTORY  OF  CHEMISTRY 

Prout,  y[,  English  physician.  Supposed  all  atoms  to  be  poly- 
mers of  hydrogen,  1815.  Also  worked  at  organic  products 
of  the  metabolism. 

Berzelius.J.J.  Baron^*]*]^- 1 848),  Swedish  apothecary,  professor 
(1802)  and  secretary  (1818)  to  the  Stockholm  Academy  of 
Sciences.  His  chief  aim  was  the  final  establishment  of  the 
laws  of  chemical  proportion,  including  the  determination  of 
atomic  weights  and  the  constitution  of  inorganic  and  organic 
compounds.  Discovered  cerium  (1803),  selenium  (1817), 
thorium  (1828),  isolated  Si  (1810),  Zr  (1824),  Ti  (1825)  ; 
worked  at  many  inorganic  compounds,  notably  those  of 
the  rarer  metals,  such  as  Ti,  Zr,  Th,  Cr,  Mo,  W,  U,  V, 
etc.  Elaborated  what  is  practically  the  present  system  of 
nomenclature  and  symbols  for  inorganic  compounds  in 
1811,  put  forward  his  electro-chemical  (dualistic)  theory 
in  1812,  and  extended  it  in  1819;  drew  up  a  table  of 
atomic  weights  in  1817,  and  a  modified  one  in  1826; 
discovered  sarcolactic  (1807),  racemic  (1832),  and  pyruvic 
acids  (1835)  as  well  as  many  other  organic  compounds  ; 
defined  iso-,  poly-  and  meta-merism,  1831  ;  contact 
theory  of  fermentation,  1834;  vastly  improved  analytical 
methods  and  general  manipulation  (introduced  use  of 
rubber  tubing,  water  baths,  gravimetric  filter-papers,  borax, 
cobalt,  and  other  blowpipe  reagents,^etc.). 

Dulong)  P.  L.  (1785-1838),  Director  of  Ecole  polytechnique, 
Paris.  Worked  on  oxides  of  nitrogen  (1816)  and  the 
reduced  oxy-acids  of  phosphorus  (1818)  ;  discovered  con- 
stancy of  specific  atomic  heats  (1821). 

Mitscherlich,  E.  (1794-1863),  Professor  at  Berlin  (1821-63). 
Discovered  isomorphism  (1819)  and  polymorphism  (1821). 
Investigated  substitution  (benzene  sulphonic  acid,  1833; 
nitrobenzene,  1834),  benzene  from  benzoic  acid  (1834), 
the  oxides  of  manganese,  lactic  acids,  and  the  allotropes 
of  sulphur  (1852).  Put  forward  a  contact  theory  of  fer- 
mentation (1836),  and  ascribed  the  formation  of  ether 
from  alcohol  to  catalysis. 

Thhmrd,  L.  J.  (1777-1857),  Professor  at  Ecole  polytechnique, 
Paris.  Worked  at  first  in  conjunction  with  Gay-Lussac  on 
processes  for  manufacturing  bleaching-powder  (i  799),  white 
lead  (1801),  and  chlorine  (1810),  discovered  H2O2  (1818), 


APPENDIX  A  215 

HF,   phosphorus    hydrides  and    preparation   of  organic 
phosphines  (1845-8). 

MODERN  (STATIC  STRUCTURAL)  PERIOD 
(a)  General  and  Physical 

Faraday,  Michael  (1791-1867),  Assistant  to  Sir  Humphrey 
Davy,  and  later  his  successor  at  the  Royal  Institution. 
Discovered  liquefaction  of  gases,  1823  ;  butylene  and 
benzene,  1825;  actinometry  ;  laws  of  electrolysis,  1833; 
discovered  magnetic  rotation  of  polarized  light,  1846. 

Regnault,  H.  V.  (1810-78),  Professor  at  Aix-la-Chapelle  and 
Paris.  Worked  on  the  composition  of  various  alkaloids 
(1840  and  1860)  ;  established  the  constitution  of  piperine, 
1863;  aliphatic  sulphonic  acids,  1840;  put  forward  the 
theory  of  "  mechanical  organic  types  " ;  variation  of  spe- 
cific heat  with  temperature,  1840  ;  measurements  of 
densities  (1845)  and  specific  heats  (Cp  and  Cv,  1853)  of 
gases. 

Deville,  H.  St.  Clair  (1818-81),  Professor  at  Paris.  Investi- 
gated inorganic  compounds  (N2O5,  1849;  halides  of  B, 
Si,  etc. ;  preparation  of  metals  from  their  chlorides  heated 
with  sodium  ;  purification  of  the  platinum  metals,  1805-9) 
and  physical  properties  (refractive  index,  1854  ;  dissocia- 
tion on  heating,  1857). 

Pasteur,  Louis  (1822-95),  Professor  at  Strassburg.  Investigated 
optical  activity  (enantiomorphous  sodium  ammonium  tar- 
trate  crystals,  1850;  resolution  of  racemates  by  mechani- 
cal means,  1850  ;  by  fractional  crystallization  with  active 
base  or  acid,  1853  ;  by  bacteria,  1860;  isogonism,  1861) 
and  biochemistry  (vitalistic  fermentation  theory,  1855  ; 
bacteriology,  1865-95;  Institut  Pasteur  at  Paris  opened, 
1889). 

Kopp,  H.  (1817-92),  Professor  at  Giessen.  Pupil  of  Liebig. 
Worked  chiefly  on  specific  volumes  (1842-1855),  boiling- 
points  (1845-60),  and  variation  of  specific  heat  with 
temperature  (1865). 

Cannizzaro,  S.,  Italian  .professor.  Faraday  lecture,  1872. 
Established  rules  Jor* determining  which  multiple  of  the 


3i6         A  SHORT  HISTORY  OF  CHEMISTRY 

equivalent  is  the  atomic  weight,  1858.     Other  work  mainly 
organic. 

TJwmsen,J.  (1826-1908),  Danish  professor  (Copenhagen).  Ex- 
tremely thorough  and  varied  thermo-chemical  investigations 
(1853-1908). 

Berthelot,  M.  (1827-1907),  Parisian  professor  and  Secretary  of 
State  ;  chemical  historian.  His  work  embraces  four 
periods:  (a)  1850-60,  constitution  and  synthesis  of  poly- 
atomic fatty  alcohols  and  acids;  (b]  1861-69,  pyrogenetic 
and  electric  arc  syntheses  of  hydrocarbons  (acetylene, 
benzene,  etc.) ;  reduction  to  hydrocarbons  by  hydriodic 
acid;  (<:)  1869-85,  extensive  thermo-chemical  investiga- 
tions, especially  dealing  with  explosives;  silent  electric 
discharge  syntheses  ;  (d)  1885-1907,  agricultural  and  his- 
torical chemistry. 

Gladstone,  f.  H.  (1827-1902),  President  Chemical  Society  ^  1877 . 
Refractive  index  of  elements  and  specific  refractive  index, 
1858;  atomic  weights,  refraction  and  dispersion  investi- 
gations, 1860-1902. 

Landolt,  H.,  Professor  at  Berlin.  Organic  As  and  Sb  compounds, 
1853;  formula  for  refractive  index,  1864;  connexion  be- 
tween refractive  index  and  periodic  law;  optical  activity 
of  electrolytes,  1863;  conservation  of  matter  re-proved, 
1893-1908. 

Meyer,  J.  Lothar  (1830-95),  Professor  at  Karlsruhe  and  Tu- 
bingen. Chemistry  of  blood,  1857;  molecular  volumes 
and  periodic  system,  1867-70  ;  compounds  of  halogens 
with  each  other,  1877-85. 

Mendelejew,  D.  I.  (1834-1907),  Professor  at  St.  Petersburg, 
1865.  Work  on  expansion  of  liquids,  1861  ;  periodic 
system,  1869;  critical  data  of  gases,  1870-85  ;  voluminous 
author. 

Horstmann,  A.  Thermo-dynamics  of  law  of  mass  action,  1869- 
7  7  ;  stated  the  simple  gas  equation  PV  =  RT ;  specific 
volumes  (1886-88). 

(b)  Inorganic 

Balard,  M.  (1802-76).  Discovered  bromine,  1826;  constitu- 
tion of  bleaching-powder,  1835. 


APPENDIX  A  217 

Graham,  T.  (1805-69),  Professor  at  Glasgow  and  University 
College,  London.  President  Chemical  Society,  1841. 
Polybasicity  of  phosphoric  and  arsenic  acids,  1 833  ;  dif- 
fusion, dialysis,  and  osmosis  (of  liquids)  and  diffusion  and 
effusion  (of  gases),  1851  ;  definition  of  crystalloids  and 
colloids,  1862. 

Rose,  H.  (1795-1864),  Professor  at  Berlin.  Hydrolysis  of 
strong  acids,  1848  ;  cobalt  ammonia  salts,  columbium 
(discovered  1846);  mineral  syntheses  and  improved  ana- 
lytical methods. 

Stas,f.  S.  (1813-91),  Professor  at  Brussels.  Very  exact  de- 
terminations of  atomic  weights,  1840-70;  toxicological 
tests,  1850;  spectra  of  alkaline  earths,  1880. 

Marignac,f.  C.  G.  (1817-94),  Professor  at  Geneva.  Constitu- 
tion of  ozone ;  thermo-chemistry  and  atomic-weight  esti- 
mations (1842-83). 

Roscoe,  Sir  H.,  Professor  at  Manchester.  President  Chemical 
Society,  1880.  Complex  inorganic  acids;  isolation  and 
compounds  of  W,  V,  etc.,  1867;  actinometry,  1857; 
spectroscopic  work,  1863  ;  atomic  weights,  etc. 

Winkler,  C.  (1838-1904),  Professor  at  Freiburg.  Gas-analy- 
sis ;  hydraulic  cements  ;  contact-process  for  H2SO4,  1875  ; 
discovery  of  germanium,  1886;  atomic  weights,  etc. 

Boisbaudran,  Lecoq  de,  Professor  at  Paris.  Discovered  Ga, 
1875;  Sm,  1879;  Dy,  1886;  Gd,  1889;  mathematical 
relations  of  spectra,  1889. 

Nilson,L*  F,  (1840-99),  Professor  at  Stockholm.  Discovered 
Sc,  1879;  atomic  weights  (Be,  Th,  Sc,  1880-2);  specific 
heats  (Dulong-Petit  Law)  and  vapour  densities  at  high 
temperatures,  1880-9. 

(c)  Organic 

Dobereiner,  J.  IV.  (1780-1849),  Professor  at  Jena.  Relation 
of  acetic  and  oxalic  acids  to  alcohol,  1821  ;  noted  series 
of  "triads"  in  the  metals  (e.g.  Ca,  Sr,  Ba,  1829);  dis- 
covered furfurol,  1831 ;  worked  on  aldehyde,  1834. 

Dumas,  J.  B.  A.  (1800-84),  Apothecary  at  Geneva  and 
later  professor  at  Paris.  Vapour-density  estimation, 
1827;  etherin  theory,  1828;  estimation  of  organic  nitro- 


2i8         A  SHORT  HISTORY  OF  CHEMISTRY 

gen,  1830;  cinnamyl  derivatives,  1834;  substitution, 
1834  ;  hydrolysis  of  nitriles  to  acids  and  amines,  1847 ; 
atomic  weights  (1856-9) ;  compositions  of  terpenes,  etc. 

Liebig,  f.  von  Baron  (1803-73),  Professor  at  Giessen  (1824), 
Munich  (1852).  Chief  work  :  on  fulminates  with  Gay- 
Lussac  (1821),  synthesis  of  urea  (1828),  chloroform 
(1831),  on  radicle  "benzoyl"  (1832),  first  radicle  theory 
(1832),  in  conjunction  with  Wohler;  polybasicity  of  acids 
(1839);  vibration  theory  of  fermentation  (1839);  investi- 
gated many  other  organic  reactions  and  compounds  during 
the  next  twenty  years,  especially  among  the  alkaloids 
(1837-41)  and  animal  products  such  as  amino-acids 
and  amides  (1846-52);  in  later  years  became  more  of  a 
physiologist  than  a  chemist. 

Wohler,  F.  (1800-82),  Professor  at  Gottingen  (1836).  Be- 
sides his  work  with  Liebig,  he  isolated  Be,  Al,  B  and  Si 
(1828);  discovered  amygdalin  (1837),  parabanic  acid 
(1838),  hydroquinone  (1848),  calcium  carbide  (1862), 
etc. ;  worked  on  metallic  sub-  and  per-oxides,  non-metallic 
hydrides  and  halides,  and  pointed  out  the  analogy  of  silicon 
to  carbon  in  organic  compounds  (1863). 

Laurent,  A.  (1807-53),  Professor  at  Bordeaux.  Discovered 
anthracene  (1832),  anthraquinone  (1835),  phthalic  acid 
(1836),  adipic  acid  (1837),  piperine  (1840),  etc.  "  Nucleus 
theory,"  1837;  definition  of  equivalent,  atom,  molecule, 
1843  5  ether  and  alcohol  correspond  to  oxide  and  hydrate, 
1846. 

Gerhardt,  C.  (1816-56),  Professor  at  Montpellier  and  Strass- 
burg.  Theory  of  residues,  1839;  of  four  types,  1853; 
atomic  weight  system ;  homologous  series,  1 844  ;  dis- 
covered quinoline  (1842),  the  anilides  (1845),  acid  chlorides 
from  POC13  (1851)  and  acid  anhydrides  (1852). 

Peltgot,  E.  M.  (1811-90),  Professor  at  Paris.  Worked  with 
Dumas  on  " cinnamyl"  (1834);  used  PC15  for  chlorina- 
tion,  18364  isolated  various  metals  of  the  uranium  group. 

Pelouze,  J.  Worked  on  the  terpene  series  (discovered  borneol, 
1841) ;  inorganic  esters  of  alcohol ;  manufacture  of  plate- 
glass,  1856. 

Ca hours,  — .  Died  in  1891.  Discovered  amyl  alcohol,  1837  ; 
anisol  and  its  derivatives,  1841  ;  phellandrene,  1841  ; 


APPENDIX  A  219 

methyl  salicylate  (in  oil  of  winter  green),  1843  ;  prepara- 
tion of  acid  chlorides  by  PC15,  1846;  allyl  alcohol,  1856; 
tintetraethyl,  1860;  alkyl  sulphonium  bases,  1865. 

Piria,  ^?.,  Professor  in  Italy.  Discovered  salicin  (1839)  and 
worked  out  the  chief  salicyl  derivatives  ;  sulphonation  by 
ammonium  sulphite  (1850);  and  estimation  of  organic 
halogens  in  the  dry  way  (1879). 

Zinin,  N.  (died  1880),  Professor  at  St.  Petersburg.  Aniline 
from  nitrobenzene  by  ammonium  sulphide,  1841  ; 
a-naphthylamine,  1842  ;  benzidine  from  nitro-benzene, 
1845  ;  azoxybenzene,  1853. 

Anderson,  T.,  Professor  at  Glasgow.  Discovered  pyridine  in 
bone-oil,  1846;  constitution  of  piperine,  1850;  prepara- 
tion of  pyrrol,  1858;  constitution  of  anthraquinone,  1861. 

Kolle,  H.  (1818-84),  Professor  at  Marburg  (1851)  and  Leipzig 
(1865).  Synthesis  of  acetic  acid,  1842  ;  methyl  sulphonic 
acid,  1845;  electrolysis  of  fatty  acids,  1850;  nature  of 
valency,  1854-65  ;  synthesis  of  salicylic  acid  (from  phenol), 
1860;  taurine,  1862;  malonic  acid,  1864  ;  aliphatic  nitro- 
compounds,  1872. 

Hofmann\  A.  W.  von  (1818-92),  Professor  at  College  of  Che- 
mistry, London  (1845)  ;  Berlin  (1865).  President  of  Che- 
mical Society,  1861  ;  founded  the  Deutschen  Chemischen 
Gesellschaft,  1868.  Amines  from  ammonia  and  alkyl 
iodides,  1850;  constitution  of  aniline,  1843;  alkylanilines 
by  alkylation,  1872;  isonitriles  from  chloroform  and  amines, 
1866  ;  myrosin  and  mustard  oil  constitution,  1868  ;  vapour 
density  method,  1868  ;  discovered  hydrazobenzene,  1863  ; 
diphenylamine,  1864  ;  formaldehyde,  1868,  etc.  etc.  Pre- 
pared numerous  dyes  (chrysaniline,  1862,'  alkyl rosanilines, 
1867-75  ;  magdalared,  1869  ;  chrysoidine,  1877),  improved 
methods  of  organic  preparation  and  analysis,  etc. 

Wurtz,  C.  A.  (1817-84),  Professor  in  Paris.  Wrote  several 
noted  chemical  books ;  discovered  POC13,  1847;  ethylene 
oxide,  1859  ;  reaction  of  amine-formation  from  alkyl  iso- 
cyanates,  1848  ;  action  of  sodium  on  alkyl  halides,  1855  ; 
reduction  of  aldehydes  to  alcohols,  1866;  and  the  aldol 
condensation,  1872. 

jFrankland,  Sir  E.  (1825-99),  Professor  in  Manchester  and 
London.  President  Chemical  Society,  1871.  Worked  on 


220         A  SHORT  HISTORY  OF  CHEMISTRY 

metallo-organic  compounds,  1849-64  ;  theory  of  atomicity 
(valency),  1853-60  ;  hydrocarbons  from  zinc  alkyls,  1849; 
constitution  of  acetoacetic  ester,  1864;  helped  to  devise 
the  modern  structure  notation,  1867. 

Strecker,  A.  (1822-71),  Professor  at  Wiirzburg.  Chief  work 
on  amino-acid  or  peptide  derivatives.  Syntheses  of  ammo- 
acids  from  1860  ;  worked  on  the  constitution  of  guanine, 
caffeine,  quinine,  etc. ;  introduced  the  method  of  ester- 
preparation  from  alkyl  halide  and  silver  salts  of  organic 
acids,  1 86 1. 

Williamson,  A.  W.  (1824-1904),  Professor  at  University  Col- 
lege, London.  Formation  and  constitution  of  the  ethers, 
1850-52  ;  synthesis  of  glycol,  1854  ;  formation  of  aldehydes 
and  ketones  by  distillation  of  calcium  salts. 

Debut)  H.,  Lecturer  at  Guy's  Hospital.  Thorough  researches 
on  the  oxidation  of  alcohol  (1856)  and  the  composition  of 
gases  evolved  from  explosives. 

Perkin,  Sir  W.  H.  (1838-1907),  President  of  the  Chemical 
Society,  1883  ;  oxidation  of  aniline  and  production  of 
mauve,  the  first  coal-tar  dye,  1856;  synthesis  of  tartaric 
acid,  1861 ;  ofcoumarin,  1865  ;  of  cinnamic  acid  ("  Parkin's 
reaction"),  1875;  constitution  of  salicin,  1868;  relation 
between  magnetic  rotatory  power  and  chemical  constitu- 
tion, 1892-1907. 

Kekule>  A.  (1829-96),  Professor  at  Geneva  (1858)  ;  Bonn 
(1865).  Added  the  methane  type  to  the  four  types  of 
Gerhardt,  1857  ;  tetravalency  of  carbon,  1858  (shared  with 
Couper) ;  benzene  theory,  1867;  azo-formula  for  diazo- 
salts,  1867  ;  possible  oscillation  of  the  fourth  valency  in  the 
benzene  ring,  1872  ;  syntheses  of  acetylene  (from  fumaric 
acid  electrolysis,  1864),  benzoic  acid  (Na  +  CO2  -f  C6H5Br, 
1866),  crotonaldehyde  and  triphenylmethane,  1872. 

Bunsen,  R.  W.  (1811-99),  Professor  at  Marburg  (1838), 
Breslau,  and  Heidelberg  (1858).  Investigated  cacodyl 
(As(CH3)2)  compounds,  1837-43  ;  production  of  cyanides 
from  alkalies  and  coal,  1847  ;  method  for  iodine  titration, 
1853;  actinometry,  1857;  distinctive  emission  spectra  of 
each  element,  1859;  discovery  of  rubidium  and  caesium, 
1 86 1  ;  invented  many  practical  devices,  e.g.  his  gas-burner, 
thermostats,  water  pumps,  etc.  etc. 


APPENDIX  A  221 

Blomstrand,  C.  W.  ( 1 8  2  6-9  7 ) .  Constancy  of  valency,  1860-65; 
complex  metallammines  ;  "diazonium  formula"  for  diazo- 
salts,  1875. 

Butkrow,  A.  M.  (1828-86),  Professor  at  St.  Petersburg.  First 
synthetic  hexoses  "  methyleneitan,"  1861 ;  production  of 
tertiary  alcohols  from  zinc  alkyls  and  acid  chlorides, 
1864;  isomeric  butylenes  and  tautomerism,  1877. 

Friedel)  C.  (1832-99),  Professor  at  Paris.  Synthesis  of  min- 
erals ;  reduction  of  ketones  to  secondary  alcohols,  1862  ; 
silicon  tetra  alkyls,  1863  ;  action  of  aluminium  chloride  on 
aromatic  hydrocarbons  with  alkyl  halides,  1877. 

Fittig,  R.  (1835-),  Professor  at  Tubingen.  Discovered  pina- 
cone  reaction,  1858  ;  action  of  sodium  on  mixed  anyl 
and  alkyl  halides,  1863;  synthesis  of  mesitylene,  1868;  of 
ketonic  esters  by  zinc  dust  and  chlorofatty  acid  esters  on 
oxalic  ester,  1887;  coumarone,  1883;  lactones  and  para- 
conic  acids  (1894-1904). 

Griess,  /  P.  (1829-88),  Chemist  at  Burton-on-Trent.  Dis- 
covered diazo-compounds,  1859-63;  diazo-amidobenzene, 
1862  ;  diazobenzeneamide,  1866  ;  Bismarck  brown,  1867  ; 
congo  yellow,  1889  ;  constitution  of  betaines,  1867  ;  orien- 
tation determination,  1872. 

Erlenmeyer,  JS.,  sen.  (died  in  1909),  Professor  at  Frankfurt. 
"Affinity  points"  cause  valency,  1863;  constitution  of 
napthalene,  1866;  final  modern  structure  notation,  1867  ; 
synthesis  of  tyrosine,  1882;  lactone  theory,  1880;  on 
cinnamic  and  iso-cinnamic  acids,  1890-  ;  relations  between 
isomeric  fatty  acids,  1898. 

Lossen,  W.  (1838-1907),  Professor  at  Kb'nigsberg.  Discovered 
hydroxylamine,  1865  ;  stereo-isomeric  imido-ethers,  1872  ; 
specific  volumes,  1882. 

Saytzew,  A.  Sulphoxides  and  sulphones,  1866;  first  lactone 
(butyro-lactone),  1873;  zinc  dust  as  condensing  reagent, 
1875;  palladium  hydride,  1872. 

Korner,  W.,  Professor  in  Italy.  Formula  for  pyridine,  1869  ; 
orientation  determination,  1874;  synthesis  of  asparagine, 
1887. 

Liebermann>  C.,  Professor  at  Berlin  Technical  College.  Action 
of  nitrous  acid  on  phenols  and  secondary  amines,  1874  ; 
anthraquinone  and  oxyanthraquinones  (alizarin),  1868-80; 


222         A  SHORT  HISTORY  OF  CHEMISTRY 

constitution  of  anthracene  and  phenanthrene,  1870; 
quercitrin,  1879;  work  on  azo-,  alizarin-,  anthracene  and 
natural  dyes. 

Grdbe,  C.,  Professor  at  Geneva.  Synthesis  of  alizarin,  1869; 
acridine,  1871;  carbazole,  1872;  constitution  of  anthra- 
cene and  phenanthrene, -1870 ;  quinoline,  1878;  euxan- 
thone,  1880  (synthesis,  1889);  on  acenapthenes,  1893; 
condensations  with  0-amidobenzophenones,  1895  ;  con- 
stitutions of  acid  decomposition  products  of  plant  dyes, 
1899-. 

Ladenburg,  A.,  Professor  at  Breslau.  "  Prism  formula "  for 
benzene,  1869  ;  equivalence  of  hydrogen  atoms  in  benzene, 
1874;  orientation,  1875;  aromatic  silicon  derivations, 
1874;  benzimidazoles,  benzoxazoles  and  glyoxalines, 
1875-8;  synthesis  of  ptomaines,  1886;  of  optically-active 
coniine,  1886;  on  the  constitution  of  atropine  and  other 
alkaloids,  since  1880. 

Jorgensen>  S.  M.,  Professor  at  Copenhagen.  Detection  of 
alkaloids  by  polyiodides,  1870  ;  constitution  and  properties 
of  metallammino  (cobalt)  salts,  1880-1908  (controversy 
with  Werner). 

Volhard,  J.,  Professor  at  Halle.  Synthesis  of  sarcosine  (1862) 
and  creatine  (1869) ;  thiocyanate  titration  for  silver  (1874)  ; 
thiophenes  from  succinates  and  P2S3  (1885). 

Nietzski,  R.y  Professor  at  Basel.  Aniline  black,  1876;  pre- 
paration of  quinones,  1877  ;  theory  of  colouring  matters, 
1879  ;  Biebrich  scarlet,  1880  ;  hexaoxybenzene  compounds, 
1885. 

MODERN  (DYNAMIC  STRUCTURAL)  PERIOD 
(ARRANGED  ALPHABETICALLY) 

(a)   General  and  Physical 

Arrhenius,  S.,  Professor  at  Stockholm.  Ionic  theory  of  elec- 
trolytic dissociation,  1886;  hydration  of  ions,  1888; 
conductivity  of  pure  water,  1893  ;  viscosity  of  electrolytes, 
etc. 

Briihl,  J.,  Professor  at  Heidelberg.  Many  investigations  into 
the  effect  of  constitution  on  refractive  index,  1880-  ; 


APPENDIX  A  223 

constitutions  of  terpene  derivatives,  1890;  refractivity  of 
benzene,  1894;  of  tautomeric  substances,  1899,  etc. 

Dewar,  Sir  J.,  Professor  at  Royal  Institution.  President 
Chemical  Society,  1897.  Formula  for  quinoline,  1871 ;  on 
liquefaction  of  gases,  1884-  ;  "vacuum  vessel"  for 
holding  liquid  air,  etc.  ;  liquefaction  of  hydrogen,  1898  ; 
charcoal  as  gas  absorbent  at  low  temperatures,  1905. 

Guye,  P.  A.,  Professor  at  Geneva.  Theory  of  quantitative 
optical  rotatory  power,  1890;  work  on  "asymmetry  pro- 
duct," 1891-9  ;  atomic  weights  from  gas-densities  and  de- 
termination of  critical  data,  compressibilities,  etc.,  1900-  . 

Nernst,  W.,  Professor  at  Gottingen  and  Berlin.  Diffusion 
theory  of  solutions,  1888;  dissociation  of  pure  water, 
1894;  dielectric  constant  determination,  1894;  quadrant 
electrometer,  1896,  etc. 

Ostwald,  W.,  Professor  at  Leipzig.  Nobel  prize,  1909.  Pyc- 
nometer  and  other  physico-chemical  apparatus,  1873-  ; 
partition  of  a  base  between  two  acids  (dilatometry  and 
refractive  power),  1878  ;  rate  of  hydrolysis  of  salts  and 
esters,  1883 ;  conductivity  of  acids,  1878-87  ;  various 
methods  of  comparing  the  relative  "  affinities "  (affinity- 
constants)  of  acids,  bases,  etc.,  1885-  ;  viscosity  of 
solutions,  1891  ;  definition  of  properties  (additive,  con- 
stitutive, colligative),  1891  ;  conductivity  of  pure  water, 
1893. 

Pope,  W.  J.,  Professor  at  Manchester  and  Cambridge. 
Synthesis  of  asymmetric  (optically-active)  nitrogen  (1899), 
tin  (1900),  sulphur  (1900)  and  selenium  (1902)  com- 
pounds ;  crystallographic  theory,  1906 ;  gold  and  platinum 
alkyls,  1908. 

Ramsay,  Sir  W.,  Professor  at  University  College,  London. 
Nobel  prize,  1904.  President  of  Chemical  Society,  1907. 
Synthesis  of  pyridine,  1877  ;  atomic  weight  of  zinc,  1884; 
improved  Hofmann's  vapour-density  method  (application 
to  varying  temperatures  and  pressures),  1885;  surface- 
tension  and  molecular  weight,  1893;  critical  data,  1894; 
the  rare  gases,  1893-1908;  radio-activity,  1903-  ;  de- 
gradation of  heavy  elements  to  lowest  member  of  their 
series,  1907-  ;  electronic  theory,  1908-9;  radium  emana- 
tion or  niton,  1910. 


224         A  SHORT  HISTORY  OF  CHEMISTRY 

jRayleigh,  Lord.  Nobel  prize,  1904.  Composition  of  water, 
1889;  re-determination  of  gas  densities,  1892-  ;  dis- 
covery of  argon,  1894;  and  other  physical  researches. 

Tschugaeff,  Z.,  Professor  at  Moscow.  Optical  rotatory  power 
in  homologous  series,  1898  ;  effect  of  <?-,  m-t  /-substitution 
on  optical  activity,  1898;  triboluminescence,  1901-5; 
work  on  terpenes,  1904- 

Van  't  If  off,  f.  H.,  Professor  at  Amsterdam.  Stereochemistry 
of  carbon  (1874)  and  nitrogen  (1878);  development  of 
law  of  mass-action,  1877;  physical  chemistry  of  dilute 
solutions,  1880;  "Etudes  de  dynamique  chimique,"  1884; 
elevation  of  b.  p.  and  depression  of  f.  p.  proportional  to 
change  of  vapour  pressure,  1886  ;  methods  for  determina- 
tion of  transition-point,  1884-92,  etc. 

Van  der  Waals^J".,  Professor  in  Holland.  Gas-equation,  1881  ; 
on  electrolytic  dissociation  formula,  1891  ;  capillarity,  1894  ; 
continuity  of  gaseous  and  liquid  states,  1899;  theory  of 
mixtures,  1906. 

Walker,  f.,  Professor  at  Edinburgh.  Electrolytic  synthesis 
of  malonic  esters,  1891  ;  periodic  system  work,  1891  ; 
hydrolysis  of  esters,  1889-93  >  boiling-points  of  homo- 
logous compounds,  1894;  conductivity  of  weak  acids, 
1900;  amphoteric  electrolytes,  1902,  etc. 

Walden,  P.,  Professor  at  Riga.  Conductivity  of  organic  acids, 
1891;  "Walden  inversion,"  1895;  unsaturation  and 
optical  activity,  1896  ;  conductivity  of  non-aqueous  sol- 
vents, 1901-6;  dielectric  constants,  1906-  ,  etc. 

Young,  S.,  Professor  at  Dublin.  Investigations  on  vapour- 
pressure,  1886-92;  relation  of  boiling-points,  molecular 
volumes,  and  other  properties  and  chemical  constitution, 
1890;  critical  data,  1893-4;  separation  of  mixtures  by 
distillation,  ^94-7. 

(b)  Inorganic 

Crookes,  Sir  W.  President  Chemical  Society,  1867.  Discovered 
thallium,  1861 ;  phenomenon  of  cathode  rays,  1880;  spec- 
troscopic  work  on  rare  earths  since  about  1880;  theories 
of  ultimate  genesis  of  matter — "protyle,"  1886;  "meta- 
elements,"  1889;  fixation  of  nitrogen,  1892. 


APPENDIX  A  225 

Curie,  M.  (1859-1906)  and  Mme.  (Professor  at  Paris,  in  her 
husband's  place).  Radioactivity  of  uranium  and  thorium 
minerals,  1902;  isolation  of  radium,  1903;  polonium, 
1903;  disintegration  of  radium,  1904-  .  M.  Curie  was 
also  noted  as  physicist  and  crystallographer. 

Lobry  de  Bruyn,  C.  A.  (1857-1904),  Professor  at  Amsterdam. 
Nitro-aromatic  compounds,  1890;  hydroxylamine,  1891; 
hydrazine  hydrate,  1894,  (anhydrous),  1896;  colloidal 
solutions,  1902. 

Moissan,  H.  (1852-1907),  Professor  at  Paris.  Nobel  prize, 
1906.  Metal  oxides,  1879-83  ;  fluorine  compounds,  1883  ; 
isolation  of  fluorine,  1886;  electric  furnace,  1892;  metal 
carbides  and  carborundum,  1893-4  ;  nitrides  ;  artificial 
diamonds  ;  reduction  of  refractory  metal  oxides,  1896  ; 
silicon  hydrides,  1902. 

(c)   Organic 

Anschiitz,  R.,  Professor  at  Bonn.  On  pyrocondensatioris, 
1878  ;  oxidation  of  fumaric  and  maleic  to  racemic  and 
mesotartaric  acids,  1880  ;  citraconic  and  isomeric  acids, 
1 88 1  ;  aluminium  chloride  syntheses,  1884  ;  stereoisomeric 
hydrazones,  1895. 

Armstrong.  H.  E.,  Professor  at  South  Kensington.  President  of 
Chemical  Society,  1 893.  Constitution  of  terpenes  and  cam- 
phors, 1871-96;  "centric"  formula  for  benzene,  1892; 
origin  of  colour,  1893  ;  electric  conductivity  and  theories 
of  solution,  1892-1902;  naphthalene-sulphonic  acids, 
1891  ;  Caro's  acid,  1902. 

Baeyer,  A.  (1835-),  Professor  at  Berlin  and  Munich.  On 
polymethylenes,  1861- ;  constitution  of  furfurol  and  pyrrol, 
1870;  indene,  1884;  orientation  of  phthalic  acids,  1871  ; 
reduction  of  benzene  and  benzoic  acids,  1887-92  ;  strain 
theory  of  carbon  ring-stability,  1885  ;  steric  formula  for 
benzene,  1888  ;  centric  formula,  1892  ;  on  purine  de- 
rivatives and  uric  acid,  1863-70;  indigo  constitution  and 
synthesis,  1866-90;  terpenes,  1890-1900,  etc. 

Bamberger,  E.,  Professor  at  Munich.  Guanidine  and  cyan- 
amide  compounds,  1880  ;  constitution  of  retene,  1884  ; 
chrysene,  1895  ;  sodium  and  amyl  alcohol  as  reducing 

15 


226          A  SHORT  HISTORY  OF  CHEMISTRY 

agent,  1887 ;  diazo-controversy  with  Hantzsch,  1895- 
1900. 

Beckmann,  £.,  Professor  at  Erlangen.  On  iso-nitroso  com- 
pounds, 1886  ;  equivalence  of  nitrogen  valencies,  1885  ; 
isomeric  benzaldoxines,  1885  ;  apparatus  and  thermometer 
for  molecular  weight  by  freezing-point  (1888)  and  boiling- 
point  methods  (1889),  etc. 

Bernthsen,  A.  Badische  Anilin  u.  Soda  Fabrik.  Methylene- 
blue  constitution,  1883  ;  safranine,  1885  ;  thiodiphenyl- 
amine  and  phenazine  syntheses,  1886  ;  acridihes,  1884-93  J 
hydrosulphurous  acid,  1905. 

Bischoff,  C.  A.  (1855-1908),  Professor  at  Riga.  Syntheses  of 
aliphatic  acids  by  ketonic  esters,  1876  ;  on  ring-formation, 
1880-88  ;  stereochemistry  of  nitrogen  atom,  1890  ;  steric 
hindrance,  1894. 

Brown,  A.  Crum,  Professor  at  Edinburgh.  President  of  the 
Chemical  Society,  1891.  Contributions  to  modern  structure 
rotation,  1865;  thetines,  1878;  quantitative  hypothesis 
for  optical  rotatory  power,  1891  ;  electrolytic  syntheses  of 
malonic  esters,  1891  ;  osmotic  pressure,  1900. 

Caro,  H.  Induline  dyes,  1865  ;  Bismarck  brown,  1867  ;  acri- 
dine  synthesis,  1871;  eosin,  1873;  monopersulphuric 
acid,  1898. 

Claisen,  L.,  Professor  at  Kiel.  Aromatic  ketonic  esters,  1880; 
benzalacetone,  1881  ;  pyrazole  synthesis,  1888  ;  /?-dike- 
tones,  1889  ;  tautomeric  substances,  1893-99. 

Collie,  J.  IV.,  Professor  at  University  College,  London. 
Action  of  heat  on  complex  ammonium  and  phosphorium 
salts,  1881-1888  ;  on  the  rare  gases,  1896  ;  space  formula 
for  benzene,  1897  ;  pyrones,  quadrivalent  oxygen,  poly- 
ketides,  etc.,  1891-1907  ;  decomposition  of  CO2  by  silent 
electric  discharge,  1901. 

Curtius,  T.,  Professor  at  Heidelberg.  Diazoacetic  ester, 
1883  ;  hydrazine,  1887  ;  hydrazoic  acid,  1890-93  ;  pyrazo- 
line  derivatives,  1894  ;  aldazine  transformations,  1900  ; 
glycocoll,  asparagine  and  polypeptide  syntheses,  1904. 

Fischer,  Emil,  Professor  at  Berlin.  Constitution  of  rosa- 
niline  and  alkylrosanilines,  1867-75  '•>  phenylhydrazine, 
1875  ;  phenylhydrazones,  1877  ;  indol  and  indazoles, 
1885  ;  sugars,  constitutions  and  syntheses,  1884-1900  ; 
glucosides,  1893  ;  configuration  of  pentoses,  hexoses, 


APPENDIX  A  227 

and  tartaric  acid  completed,  1894  ;  constitution  and 
syntheses  of  the  purines,  1881-1901  ;  syntheses  of  poly- 
peptides,  1900;  discovery  of  proline,  1899. 

Gattermann,  L.,  Professor  at  Heidelberg.  On  nitrogen 
chloride,  1888 ;  alkylene  phenol  ethers,  1889  ;  liquid 
crystals,  1890 ;  copper  powder  and  diazo-compounds, 
1890;  electrolytic  reduction  of  nitro-compounds,  1893; 
sulphination  by  diazo-compounds,  1898 ;  thio-anilides, 
1899;  aldehydes  by  Grignard  reagent,  1904. 

Hantzsch,  A.,  Professor  at  Leipzig.  Pyridines  from  aldehyde 
ammonia,  1882  ;  coumarone  syntheses,  1886  ;  theory  of 
stereo-isomeric  oximes,  1890 ;  phenylnitromethane  and 
conductivity  of  ^-acids  and  ^-bases,  1896  ;  hyponitrous 
acid,  1896. 

Haller,  A,,  Professor  at  Paris.  Syntheses  from  cyano-fatty 
esters,  1888  ;  on  camphor  and  borneol,  1889-1906  ;  con- 
stitution of  camphoric  acid,  1 893 ;  partial  syntheses 
of  borneol  (1891)  and  camphor  (1895) ;  effect  of  un- 
saturation  (1899)  and  ring-formation  (1905)  on  optical 
activity. 

Kipping,  F.  S.,  Professor  at  Nottingham.  Hydrindene  de- 
rivatives, 1893-1904  ;  sulphonic  derivatives  of  camphor, 
1895  ;  keto-hexamethylenes,  1897  ;  organic  silicon  de- 
rivatives, 1904-. 

Knoevenagel,  £.,  Professor  at  Heidelberg.  Dihydroresorcinol, 
1894;  S-diketones,  1894;  terpene  syntheses,  1896;  con- 
densation of  aldehydes  and  malonic  ester,  etc.,  by  weak 
bases,  1899;  pyridine  syntheses,  1898;  moto-isomerism, 
1903  ;  sulphination,  1908. 

Rnorr,  Z.,  Professor  at  Jena.  Pyrazolone  and  antipyrine  syn- 
theses, 1883;  quinoline  syntheses,  1886;  pyrazole  syn- 
thesis, 1887  ;  tautomerism  of  methylpyrazole  and  of  ben- 
zene, 1894;  morphine  alkaloids,  1890;  tautomerism  of 
diacylsuccinic  esters,  1896-  . 

Le  Bel,  J.  Stereochemistry  of  carbon,  1874;  attempts  to 
make  optically  active  benzene  compounds,  1882  ;  stereo- 
chemistry of  nitrogen,  1891;  optically  active  asymmetric 
nitrogen,  1900. 

Marckwald,  W.,  Professor  at  Berlin.  Furfurane  compounds, 
1888;  glyoxalines,  1892;  tautomerism,  1895;  stereo- 


228         A  SHORT  HISTORY  OF  CHEMISTRY 

chemistry  of  nitrogen,  1900;  optical  activity  without 
atomic  asymmetry,  1906;  radio-activity,  1903- 

Menschutkin,  N.  (1842-1907),  Professor  at  St.  Petersburg. 
Contributions  to  law  of  mass  action  (velocities  of  ester- 
formation  and  other  organic  reactions  ;  effect  of  constitution 
on  the  rate  of  reaction). 

Meyer,  Victor  (1848-97),  Professor  at  Heidelberg.  Aliphatic 
nitro-compounds,  nitroso-compounds  and  nitrols,  1872; 
vapour-density  method,  1878 ;  iso-nitroso-compounds, 
1882  ;  thiophene,  1883;  isomeric  oximes,  1883;  steric 
hindrance,  1891-4  ;  ester  ifi  cation  and  saponification  "laws," 
1895  ;  iodoso-,  iodo-  and  iodonium  compounds,  1895. 

Perkin,  W.  H.,  Professor  at  Manchester.  Berberine,  1889; 
tetramethylene  compounds,  1894;  hexamethylene  syn- 
thesis, 1894  ;  oxidation-products  of  camphor,  1895- 
1902;  braziline  and  haematoxylin,  1900-7;  syntheses  in 
the  terpene  series,  1905-  ;  brucine  and  strychnine,  1910. 

Thiele,  J.,  Professor  at  Munich.  Guanidine  derivatives,  1902  ; 
tetrazole  derivatives,  1895;  nitramide,  1897;  theory  of 
"  partial  valencies,"  1899;  unsaturated  lactones,  1902. 

Von  Pechmann,  H.  (1850-1803),  Professor  at  Tubingen.  On 
anthraquinone,  1880;  coumarin-syntheses,  1883;  a-dike- 
tones,  1887  ; /-xyloquinone  from  diacetyl,  1889;  diazo- 
methane,  1894;  preparation  of  hydrazine,  1895. 

Wallach,  O.,  Professor  at  Gottingen.  Extensive  work  in  the 
terpene  series,  1887- 

Willstatter,  R.,  Professor  at  Munich.  Tropic  acid,  tropine 
and  atropine,  1895-1903;  ecgonine  and  cocaine,  1897- 
1903;  lecithin,  1904;  0-quinones,  pyrones,  1905;  chloro- 
phyll, 1907-  . 

Wislicenus,  J.  (1835-1902),  Professor  at  Wiirzburg  and 
Leipzig.  On  aldehyde-ammonia  condensations,  1859 ; 
lactic  acids,  1861-1873  ;  oxyacids  from  cyanhydrins,  1862  ; 
ketonic  and  other  organic  ester  syntheses,  1869-82  ;  alkyl- 
acetoacetic  esters,  1883  ;  stereochemistry,  "Die  raumliche 
Anordnung  der  Atome,"  1887  ;  pentamethylene  syntheses, 
1895. 


APPENDIX  B 


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Conrad  on  syntheses  from  malon 
Hofmann  discovered  quercite. 
E.  Fischer  prepared  the  first 
hvdrazone. 
Pfeffer  on  osmotic  pressure. 
Pictet  and  Cailletet  on  liquefai 
gases. 
Wislicenus  commenced  studies 
^rans-isomerism. 
V.  Meyer's  vapour  density  mett 
E.  and  O.  Fischer  on  rosaniline 

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242         A  SHORT  HISTORY  OF  CHEMISTRY 


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Ladenburg  synthesized  coniine. 
Ladenburg  synthesized  ptomaines. 
Loew  obtained  formose  from  form; 

hyde. 
Moissan  isolated  fluorine. 
Piutti  discovered  <f-asparagine. 
Baeyer  commenced  to  work  out 
reduction  products  of  benzene. 
E.  Fischer  prepared  a-acrose  (dl- 

tose). 
Knorr  prepared  derivatives  of  pyra: 
Piutti  and  Korner  synthesized  aspai 
Behrend  and  Roosen  synthesized 
acid. 

Raoult  on  determination  of  molei 
weight  by  depression  of  free; 
point. 
Beckmann  on  determination  of  n 
cular  weight  by  elevation  of  boi 
point. 
E.  Fischer  synthesized  rf-glucose. 
Lehmann  on  liquid  crystals. 

Le  Bel  resolved  a  compound  con 
ing  asymmetric  nitrogen. 

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Dewar  liquefied  hydrogen. 
E.  Fischer  synthesized  guanine 

punne. 
Ramsay  and  Travers  isolated  i 

krypton,  xenon. 
Ruff's  method  of  sugar-synthesis. 
Barbier  on  magnesium  and  m 
iodide. 
Collie  and  I'ickle  discovered  oxo 

salts. 
E.  Fischer  discovered  proline. 
E.  Fischer  synthesized  caffeine. 
Marchlewski  synthesized  cane-sug 
Gomberg  on  triphenylmethyl. 
Grignard's  reagent  discovered. 
E.  Fischer  commenced  work  on 
peptides. 
Loeb's  electrolytic  reduction  of  i 
benzene. 

Smiles  (and  Pope  and  Peachey)  resi 
a  compound  containing  asymn: 
sulphur. 
E.  Fischer  synthesized  proline. 
Marckwold  and  M'Kenzie's  first  a 
metric  synthesis. 

Willstatter  synthesized  atropine. 
Traube  synthesized  uric  acid,  xant 
caffeine,  etc. 

D 

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APPENDIX  B 


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and  Neville  resolved  asymmetr 
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'.  Armstrong  on  constitution  < 
[ysaccharides. 
ig  on  colloids, 
kwald  isolated  polonium, 
ing's  work  on  organic  silicon  dei 
ives  commenced, 
ctet  synthesized  nicotine. 

i.  Perkin,  jun.,  commenced  sy 
;sis  of  terpenes  by  aid  of  Grignarc 
gent. 

len  on  ionising  media. 

more  and  Stewart  isolated  keten. 
itatter  and  Veraguth  isolated  cycl 
ane. 

sky  isolated  cyclononane. 
;rlingh  Onnes  liquefied  helium. 

ww.  »JMVU««*.«»U  pa^avtimt. 

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INDEX  OF  NAMES 


[The  figures  in  black  type  refer  to  the  "  Biographical  Index  of  Chemists" 
Appendix  A.] 


ABEGG,  55,  181,  245. 

Abel,  170,  171. 

Achard,  161,  230. 

Adam,  161. 

Aders,  150. 

Agricola,  65,  125,  156. 

Albertus  Magnus,  29,  45,  65. 

Amagat,  173. 

Ampere,  62,  173. 

Ampere  Electric  Co.,  163. 

Anaximenes,  27. 

Anderson,  qi,  92, 123,  140,  141,  219, 

236. 

Andreocci,  92,  135. 
Andrews,  72,  174,  191,  239. 
Angeli,  71. 

Anschiitz,  in,  125,  198,  225. 
Arago,  in. 
Archimedes,  182. 
Aristotle,  27. 
Arfvedson,  69,  232. 
Argand,  161. 

Armstrong,  E.  F.,  145,  153,  245. 
Armstrong,  H.  E.,  72,  97,  143,  225, 

243- 
Arrhenius,    57,   61,    177,    193,   222, 

242. 

Atkinson,  143. 
Atterberg,  143. 
Aussedot,  165. 
Auwers,  103. 
Avogadro,  35,  36,  81,  173,  179,  232. 

BACON,  n. 

Badische  Aniltn   und  Soda    Fabrik, 

1 60,  169,  199,  200,  226. 
Baeyer,  72,  91,  92,  93,  94,  95,  96, 

97,  100,  102,  109,  no,  118,  122 

124,  125,  127,  129,  131,  135 


142,  143,  148,  150,  151,  169, 

I7O,     183,     199,     2OO,    204,    225, 

238, 239, 240, 241, 242, 243. 

Baker,  194,  208. 

Baker,  Miss,  55. 

Balard,  62,  70,  121,  160,  216,  233. 

Balmer,  186,  241. 

Baly,  96,  105,  187,  245. 

Bamberger,  93,  97,  in,  135,    199, 

225. 

Barbier,  130,  142,  143,  244. 
Barlow,  176,  245. 
Barnal,  141. 
Barreswil,  72. 
Barth,  200. 
Bartoletti,  146. 
Baskerville,  165. 
Baumann,  130,  150,  151,  204. 
Baubigny,  207. 

Bechamp,  124,  127,  170,  199,  200. 
Becher,  15,  29,  152,  210. 
Beckett,  141. 
Beckmann,  54,  no,  143,  181,  190, 

198,  226,  242. 
Becquerel,  74,  243. 
Behrend,  151,  242. 
Beilstein,  119;  183,  199,  200. 
Benckiser,  120. 
Bendant,  175. 
Benedicks,  74. 
Benedikt,  201. 
Bennett,  188. 
Bergmann,    16,   45,  46,  66,  70,  77, 

198,  201,  202,  211. 
Berkeley,  Earl  of,  181. 
Bernoulli,  173. 
Bernthsen,   72,    131,  134,  135,  170, 

226. 
Bertagnini,  125,  200,  204. 


>47) 


248 


A  SHORT  HISTORY  OF  CHEMISTRY 


Berthelot,  M.,  47,  67,  72,  85,  93, 
117,  118,  120,  143,  162,  170, 
175,  189, 190,  igi,  192, 193,  199, 
216,  237,  238,  239. 

Berthelot,  D.,  173,  179. 

Berthollet,  19,  46,  47,  60,  160,  171, 
192,  202,  212,  213,  231. 

Bertrand,  143. 

Berzelius,  3,  19,  31,  32,  35,  36,  37, 
42,  46,  50,  51,  56,  60,  62,  63,  65, 
66,  67,  68,  69,  70,  72,  77,  78,  79, 
80,  81,  83,  84,  86,  123,  125, 126, 
137,  152,  176,  189,  198,  201, 
202,  203,  206,  207,  214,  232, 

234- 

Besanez,   146. 
Bessemer,  156,  157,  237. 
Betti,  103. 
Bigelow,  195. 
Billitzer,  179. 
Biltz,  180,  193. 
Bineau,  102,  128. 
Biot,  in,  232. 
Bird,  159,  243. 
Birkeland,  162,  245. 
Bischoff,   107,    115,   126,   226,  241, 

242. 
Black,  13,  16,  17,  18,  19,  20,  62,  64, 

190,  202,  211,  230. 
Bladin,  92. 
Blomstrand,  53,  54,   in,  199,  221, 

240. 

Blumlein,  134. 
Blumenthal,  161. 
Bocklitch,  151. 
Borodine,  200. 
Bottger,  199. 
Bottinger,  134. 
Bouchardat,  143,  151,  235. 
Boullay,  79. 
Boyle,  2,  7,  n,  12,  13,  14,  17,  18, 

23,  29,  30,  32,  34,  62,  81,  120, 

160,    172,   173,    188,   201,  202, 

2IO,  229. 

Braconnot,  124,  147,  150,  171,  233. 
Bradge,  157. 
Brand,  70. 
Brandt,  70. 
Bredig,  179,  245. 
Bredt,  124,  142,  143. 
Brieger,  151,  241, 


Brin,  158,  241. 

Brisson,  204. 

Brodie,  124,  238. 

Brown,  A.,  153. 

Brown,  Crum,  88,  92,  113,  192,  226, 

238,  242. 
Brown,  H.,  153. 
Bruce,  94. 
Briicke,  139,  178. 

Bruhl,  96,  zoo,  101,  103,  142,  143, 

185,  222. 

Brunner,  157,  159. 
Bruylants,  143. 
Bucherer,  72. 

Buchner,  92,  119,  153,  243. 
Buckton,  130. 
Buffon,  46. 
Bunsen,  67,  69,  79,  129,  130,  157, 

163, 164, 170,  186,  188,  197,  198, 

205,  220,  235,  237,  238. 
Burgess,  188. 
Bussy,  130. 
Butlerow,   104,   117,  119,  120,  144, 

221,  238,  240. 
Buys-Ballot,  175. 

CADET,  129. 

Cagniard  de  la  Tour,  152,  174,  233, 

235- 
Cahours,  120,  121, 124, 125,  130,  143, 

150,  185,  218. 
Cailletet,  174,  240. 
Cain,  245. 
Cannizzaro,  38,  120,  179,  205,  215, 

237- 

Carius,  204. 
Caro,  H.,  72,  91,  127,  169,  170,  226, 

239,  240. 

Caro,  N.,  163,  245. 
Carlisle,  24,  231. 
Carrara,  178. 

Castner,  157,  158,  159,  241,  242. 
Cavendish,  13,  16,  18,  20,  21,  23,  24, 
26,  62,  197,  206,  211,  212,  230. 
Caventou,  140,  141,  233. 
Cazeneuve,  102. 
Champion,  171. 
Chance,  159. 
Chancel,  121. 
Chapman,  188. 
Chaptal,  19,  20, 


INDEX  OF  NAMES 


249 


Charles,  173,  231. 

Chevreul,  120,  139,  146,  162,  234. 

Chick,  126. 

Chiminello,  194. 

Chiozza,  200. 

Christensen,  65. 

Ciamician,  94. 

Claisen,  103, 122,  123,  125,  127,  135, 

226,  241,  243. 
Clarke,  207. 
Classen,  202. 

Glaus,  70.  97,  106,  170,  239. 
Clausius,  56,  173,  237. 
Clayton,  167,  229. 
Clement,  189. 
Clerget,  204. 
Cleve,  73. 
Clifton,  186. 
Cock,  156. 

Cohen,  114,  115,  196. 
Cole,  150. 
Collie,  91,  96,99,  100,  125,  143,  203, 

226,  243,  244,  245. 
Combes,  123. 
Conrad,  124,  126,  240. 
Constan,  72. 
Coppet,  i8r. 
Cort,  156,  231. 
Cosak,  199. 

Couper,  87,  88,  89,  220,  237. 
Courtois,  70,  168,  232. 
Crafts,  118,  130,  198,  239,  243. 
Cramer,  150. 
Crawford,  65. 
Crew,  65,  69. 
Croll,  65. 
Cronstedt,  70,  201. 
Crookes,  43,  69,  73,  162,  186,  224, 

238,  242. 
Crossley,  119. 

Curie,  74,  75,  175,  194,  225,  245. 
Curtius,  71,  128,  147,  226,  241. 

DAGUERRE,  188. 

Daimler,  122. 

Dale,  169,  185,  237. 

Dalton,  3,  19,  32,  33,  34,  35,  41,  49, 

66,  77,  87,  173,  205,  206,  213, 

232. 

Daniell,  51. 
Davy,  E,,  117,  235. 


Davy,  Sir  H.,  3,  19,  30,  35,  46,  49, 
50,  56,  61,  62,  69,  71,  73,  76, 
157,  166,  190,  213,  215,  232. 

Davy-Henault,  192. 

Deacon,  158,  241. 

Debierne,  75. 

Debray,  70,  156. 

Debus,  92,  121,  123,  125,  170,  199, 
220. 

De  Hemptinne,  163. 

De  la  Rive,  156,  235. 

De  la  Roche,  189. 

D'Elhujar,  70. 

Delisle,  203. 

Del  Rio,  70. 

Demarsay,  73. 

Democritus,  28. 

De  Nehan,  164. 

Dennstedt,  203. 

Derosne,  141,  231. 

Desch,  105. 

Desfontaines,  114. 

Designolles,  171. 

Desormes,  189. 

Dessaignes,  124,  125,  139,  150. 

Deville,  70,  71,  72,  143,  156,  157, 
174,  175,  185,  215,  237. 

De  Vries,  180. 

Dewar,  22,  91,  150,  174,  223,  239, 
244. 

Dickinson,  165. 

Diehl,  122. 

Diels,  126. 

Diesbach,  168. 

Dimroth,  128. 

Dioscorides,  198. 

Divers,  71. 

Dixon,  194. 

Dobbie,  187. 

Dodge,  143. 

Dobereiner,  38,  71,  92,  123,  125,217, 

234- 

Dobner,  169. 

Don  Antonio  de  Ulloa,  70. 
Donnan,  194. 
Dorant,  189. 
Douglas,  156. 
Dowson,  163,  166. 
Drechsel,  125. 
Dreher,  130. 
Drewson,  169, 


250 


A  SHORT  HISTORY  OF  CHEMISTRY 


Drude,  184. 

Dubrunfaut,  146. 

Duhamel,  6g,  229. 

Dulong,  3,  36,  71,  72,  189,  190,  206, 
214,  217,  233. 

Dumas,  37,  39,  42,  50,  51,  79,  80, 
82,  86,  93,  120,  121,  122,  124, 
125,  143,  166,  179,  199,  200, 
203,  206,  207,  217,  218,  233, 

234, 235,  236. 

Dunstan,  A.  E.,  183,  196. 
Dunstan,  W.  R.,  146. 
Duppa,  124,  125,  150,  200,  237. 
Dutrochet,  137. 
Dyar,  159. 

EARP,  183. 

Edinger,  204. 

Egerton,  44. 

Einhorn,  122,  141. 

Ellinger,  150,  151. 

Elsmore,  156. 

Emmerling,  91,  153,  164. 

Empedocles,  27. 

Engler,  189. 

Eotvos,  183. 

Epicurus,  28. 

Erdmann,  133,  207. 

Erlenmeyer,  53,   88,    93,    102,    124, 

128,  147,  150,  199,  221,  241. 
Esson,  194. 
Euler,  143. 
Eyde,  162,  245. 

FAHLBERG,  130,  241. 

Faraday,  3,  57,  77,  80,  89,  117,  121, 
168, 174,  185,  215,  233,  23  4, 236. 

Farmes,  163. 

Favre,  191. 

Fehling,  123,  124,  144,  236. 

Fenton,  146,  201. 

Picks,  178. 

Figuier,  161. 

Firmicus,  J.,  6. 

Fischer,  E.,  113,  122,  128,  135,  140. 
142,  144,  145,  146,  147,  148, 
150,  151,  169,  199,  200,  204 
226,  240,  241,  242,  243,  244. 

Fischer,  O.,  169,  240. 

Fittig,  93,  117,  118,  120,  122,  124 
135,  221,  237,  238,  243. 


Fleck,  130,  243. 
"ontaine,  171. 

'ourcroy,  19,  66,  137,  151,  213. 
7orster,  102. 
7ranchimont,  170. 
7ranke,  65. 
Frankland,  52,  53,  83,  86,  88,  101, 

117,    122,    124,    130,    166,   219, 

236,  237. 
?raunhofer,  187. 
^remy,  62,  65,  200. 
7resenius,  201,  202. 
Friedel,  67,  118,  119,  120,  130,  221, 

239. 

?riedrich,  173,  244. 
Friend,  55. 
Friedlander,  134. 
Freund,  94,  118,  121,  140,  141. 
Fritzsche,  125,  128,  235. 
Fuchs,  176. 

GADOLIN,  73,  175. 

Gahn,  62,  70. 

Gal,  200. 

Galvani,  49. 

Gamgee,  150. 

Garden,  93,  233. 

Gattermann,  72,  118,   121,  175,  200, 

201,  227,  243. 
Gautier,  128. 
Gay-Lussac,  3,  33,  35,   36,  60,  62, 

69,    71,    72,  73,  78,  79,  80,  86, 

125,    157,    160,    161,    173,  175, 

180,    182,   203,    204,    205,  213, 

214,  218,  232,  233. 
Geber,   8,   28,   29,  62,  64,  65,  125, 

209,  210. 
Geiger,  141. 
Geissler,  203. 
Gengembre,  71. 
Geoffrey,  45. 
Gerhardt,  37,  53,  81,  82,  83,  84,  85, 

86,  87,  91,  102,  124,  130,  218, 

220,  235,  236,  237. 
Gerlich,  146. 
Geuther,  101,  238. 
Gibbs,  Wolcott,  68,  195,  240. 
Giesecke,  141,  233. 
Giesel,  75. 
Gilchrist,  156, 
Girard,  199, 


INDEX  OF  NAMES 


251 


Gladstone,  47,  143,  185,  216,  237. 
Glauber,   45,   62,   65,  73,  159,  168, 

212. 

Glover,  160. 

Gmelin,  37,  150,  168,  233. 
Gnehm,  169. 
Goldschmidt,    109,    no,   143,    158, 

244. 

Gomberg,  119,  244. 
Gooch,  202. 
Goodyear,  166,  235. 
Gossage,  159. 
Grabe,  91,  93,  102,   131,    169,    170, 

199,  200,  222,  239,  240. 
Graham,  61,  63,  82,  178,  191,  217, 

234.  237,  238. 
Gray,  206,  207. 
Green,  205. 
Gregor,  69. 
Grier,  120. 
Griess,  96,  in,  118,  128,  151,  169, 

170,  200,  221,  238,  240. 
Grignard,  119,  121,    122,    124,  128, 

130,  131,  142,  227,  244,  245. 
Groth,  176. 
Grotthus,  56. 
Guimet,  168. 

Guldberg,  47,  48,  180,  192,  239. 
Gustavson,  123,  200. 
Guthrie,  195. 
Guye,   113,  114,   173,  206,  207,  223, 

242,  244. 

HAARMANN,  123. 
Haber,  191. 
Hadrich,  115. 
Haitinger,  75. 
Hall,  67. 

Haller,  114,  115,  143,  227,  243. 
Halliday,  161. 
Hampson,  22,  174,  24.3. 
Hansen,  72. 

Hantzsch,  71,   103,    1:0,   in,    133, 
178,  200,    205,    226,   227,    242, 

243- 

Harcourt,  194. 
Hargreaves,  159,  243. 
Harries,  142,  143,  166. 
Hartley,  96,  104,  181,  187. 
Hartmann,  200. 
Hatchett,  70. 


Hatfield,  71. 

Hautefeuille,  193. 

Hauy,  66,  175. 

Heintz,  204. 

Helmholtz,  139,  191. 

Hemmelmayer,  92. 

Hemming,  159. 

Hempel,  205. 

Hendrixson,  193. 

Hennel,  121. 

Henrichsen,  184. 

Henry,  33,  54,  146,  183,  195,  205. 

Hepp,  169. 

Herapath,  173. 

Hermann,  123,  124. 

Herrmann,  102. 

Hermes  Trismegistus,  7. 

Heroclitus,  27. 

Herschel,  112,  186. 

Hess,  190,  191,  235. 

Hesse,  141,  143,  234. 

Hessel,  175. 

Heumann,  169,  200. 

Hewitt,  187,  205,  244. 

Heydwiller,  178. 

Hilditch,  115,  130. 

Himly,  143. 

Hinsberg,  132,  134. 

Hittorff,  68,  177,  237. 

Hjelm,  70. 

Hjelt,  195. 

Hlasiwitz,  102,  120. 

Hobrecker,  132. 

Hobson,  102,  130. 

Hoffmann,  210. 

Hofmann,  A.  W.,  84,  85,  86,  102, 
106,  117,  120,  123,  127,  128, 
129,  130,  141,  145,  146,  151, 
168,  169,  170,  180,  199,  201, 
219,  223,  236,  239,  240. 

Hollwachs,  182. 

Homberg,  14,  62,  69. 

Homer,  62. 

Hope,  69. 

Hopkins,  150. 

Horbaczewski,  151. 

Horstmann,  48,  96,  173,  182,  2l6. 

Howard,  162,  171. 

Howbres,  162. 

Hiibner,  132. 

Hunt,  156. 


252 


A  SHORT  HISTORY  OF  CHEMISTRY 


Hutchison,  162. 
Hypatia,  6,  8. 

IPATIEW,  143. 
Isay,  151. 

JACKSON,  121. 

Jacobi,  156. 

Jacobson,  101. 

Jager,  184. 

Jahns,  151,  186. 

James,  201. 

Japp,  92,  126. 

Jellet,  193. 

Jessup,  44. 

Jobst,  151. 

Johnson,  143. 

Jolly,  178. 

Jones,  115,  178. 

Jorgensen,  54,  55,  65,  140,  222. 

Joule,  172,  173,  191. 

Judson,  194. 

Jungfleisch,  193. 

KAHLENBERG,  178,  184. 

Kaiser,  162. 

Kalle,  130. 

Kamp,  189. 

Kane,  117,  118,  143,  235. 

Kannonikow,  142,  143. 

Kapfer,  203. 

Kast,  130. 

Kauffmann,  58,  187,  243. 

Kay,  85,  120,  143,  237. 

Kayser,  43,  186. 

Kehrmann,  106,  187. 

Kekute,  53,  82,  85,  86,  87,  88,  89, 
QO,  95,  96,  98,  99,  100,  108,  in, 
113,  117,  118,  122,  123,  125, 
128,  129,  130,  143,  150,  170, 
174,  192,  200,  220,  230,  239. 

Kellas,  106. 

Kellner,  158,  159,  241. 

Kelvin,  Lord,  183,  191. 

Kestner,  125,  161,  233. 

Kiliani,  144,  146,  241. 

Kipping,  115,  116,  130,  227,  245. 

Kirchhoff,  69,  186,  237,  238. 

Kjeldahl,  150,  204,  241. 

Klages,  115. 


(  Klaproth,  66,  69,  70,  73,  125,  201, 

202,  213,  231. 
Klinger,  54. 
Knap,  153,  165. 
Knietsch,  160. 
Knoblauch,  194. 
Knoevenagel,  99,  118,  126,  227. 
Knop,  150. 
Knorr,  92,   98,  102,    103,  104,  133, 

135,  140,  141,  227,  243. 
Koch,  146. 
Kohler,  130. 

Kohlrausch,  177,  178,  182. 
Kolbe,  52,53,  83,  84,  117,  n8,  122, 

125,   127,    128,    130,    137,    150, 

192,  201,  219,  236,  238,  240. 
Kondakow,  142. 
Konigs,  140,  141,  199. 
Koninck,  146. 
Konowalow,  196. 
Kopp,  174.  176,  182,   183,  190,  215, 

236. 
Korner,   89,   91,   95,  96,    150,   221, 

239,  240. 

Kossel,  150,  151,  241,  243. 
Kostanecki,  St.  Von,  91,    136,  170, 

243- 

Kramer,  93. 
Kruger,  54,  143. 
Kriiss,  187. 
Kiihne,  139. 
Kundt,  22,  189. 
Kunkel,  7, n,  14,  29,  81,  210. 
Kuster,  105,  178. 

LAAR,  100,  104,  241. 

Ladenburg,  92,  95,  96,  97,  118,  130, 

133,    134,    !40,    I41.  I5ri   222, 

239,  240,  242. 
Lampadius,  129,  201,  231. 
Landolt,    115,    129,    172,    183,    185, 

2l6,  243. 

Laplace,  182,  190. 

Lapworth,  104,  105,  122,  244,  245. 
Lassaigne,  125,  203. 
Lautemann,  200. 
Laurent,  August,  38,  52,  80,  81,  82, 

84,  86,  93,  120,  123,  125,  140, 

141, 168,  201,  218,  234,  235,  236. 
Lauroguais,  121. 
Lauth,  169. 


INDEX  OF  NAMES 


253 


Lavoisier,  3,  u,  ig,  20,  23,  24,  25, 
26,  30,  31.  32,  50.  59.  60,  62,  63, 
71,  76,  78,  137,  152,  166,  172, 

IQO,     202,    203,     205,     2IO,    211, 
212,  230,  231. 

Lawrence,  122. 

Lawrie,  207. 

Le  Bel,  108,  112,  113, 115,  125,  227, 

240,  242. 

Leblanc,  159,  231. 
Lebrun,  167. 

Le  Chatelier,  155,  165,  189,  193. 
Lecoq  de  Boisbaudran,  69,  73,  186, 

217. 

Leduc,  179,  206. 
Lefebre,  162. 
Lehmann,  175,  242. 
Leidie,  65. 
Lellman,  193. 
Lemoine,  193. 
Le   Rossignol,    107,    118,  130,  194, 

200. 

Leser,  143. 
Letts,  92. 

Leuchs,  139,  153,  234. 
L£vy,  67. 

Lewkowitsch,  113. 
Libavius,  65,  120,  156. 
Liebermann,  93,  128,  141,  146,  169, 

170,  201,  204,  221,  239. 
Liebig,  52,  61,  62,  63,  65,  77,  78,  79, 

80,  82,  86,   102,  120,  121,  122, 

123,    124,    125,    138,    139,   140, 

141,    146,   147,    148,    150,    151, 

152,     153,     171,     198,    200,     203, 

204,  215,  218,  233,  234,  235, 
236,  239. 

Liebreich,  92,  147,  151. 
Limpricht,  92,  150,  200,  204. 
Linde,  22,  174,  243. 
Linebarger,  179,  182. 
Lippmann,  188,  199. 
List,  143. 
Lister,  120,  239. 
Lob,  127,  244. 
Lobry  de  Bruyn,  71,  225. 
Lockyer,  22,  43,  186. 
Loew,  144,  242. 
Lorentz,  185,  241. 
Lorenz,  185,  241. 
Lorin,  199. 


Lessen,  54,  71,  HI,  141,  182,  221, 

240. 

Lowenherz,  193. 
Lowig,  129,  130. 
Lowry,  72,  104,  105,  245. 
Lucretius,  28. 
Ludwig,  139. 
Liilin,  113. 
Lully,  120. 
Lunge,  167,  200,  205. 
Luther,  188. 

MACDONALD,  130. 

Mackay,  162. 

Macquer,  164,  168. 

Magnus,  65,  121,  139. 

Mallerot,  161. 

Mallet,  207. 

Marcet,  151,  232. 

Marchand,  207. 

Marchlewski,  146,  244. 

Marckwald,  75,  114,  183,  208,  227, 

244,  245. 
Marggraf,   62,    69,    156,    161,    186, 

198,  201,  202,  210,  230. 
Margueritte,  65,  205. 
Mariotte,  172. 
Marignac,  42,  65,  72,  73,  191,  206, 

207,  217. 

Markownikow,  94. 
Marshall,  72. 
Martin,  156. 
Martius,  169,  199. 
Matthey,  156. 
Mathesius,  203. 
Maxwell,  173,  186. 
Mayer,  146,  172,  189. 
Mayow,  13,  15,   17,  18,  19,  20,  25, 

210,  229. 
McDougall,  162. 
McKenzie,  114,  124,  244. 
McMillan,  no. 
Medicus,  151. 
Mehrer,  163. 
Meissheimer,  153. 
Meissner,  162. 
Melsens,  125. 
Mendius,  127. 
Mendelejew,  39,  41,  69,  70, 174,  177, 

2x6. 

Menschutkin,  228. 


254         A  SHORT  HISTORY  OF  CHEMISTRY 


Merck,  141,  236,  241. 

Merling,  141. 

Merz,  91. 

Messel,  200. 

Messinger,  203. 

Meyer,  E.  von,  51,  131. 

Meyer,  Lothar,  30,  183,  200,  216. 

Meyer,  R.,  139,  187. 

Meyer,   Victor,   92,   105,    106,    109, 

113,    122,  127,    129,    180,    199, 

228,  240,  241,  243. 
Michael,  126,  129,  130,  200. 
Michaelis,  115. 
Miller,  141,  186. 
Mitscherlich,  36,65,  68,  77,  84,  117, 

121,    128,    130,    152,    170,    175, 

176,  179,    206,    214,    233,   234, 

235- 

Moore,  22. 
Mohr,  205. 
Moir,  44. 
Moissan,  67,  70,  71,  72,  158,    163, 

225,  242,  243. 
Moldenhauer,  165. 
Mond,  159. 
Morin,  143,  164. 
Morley,  179. 
Morveau,  Guyton  de,  30,  159,  212, 

231. 

Mosander,  67,  73. 
Miiller,  200. 
Mulliken,  192. 
Murdoch,  167,  231. 
Muspratt,  159,  170. 

NAPOLEON,  212. 

Natanson,  193. 

Nef,  153. 

Neilson,  156,  234. 

Nernst,  47,  178,  184,  191,  193,  195, 

223. 

Neri,  163. 
Neuberg,  146. 
Neumann,  190,  237. 
Neville,  116,  245. 
Newberry,  165. 
Newlands,  39,  238. 
Newton,  46. 
Nicholson,  24,  231. 
Niemann,  141. 
Niepce,  188. 


Nietzski,  120,  169,    187,    199,   222, 

241. 

Nilson,  69,  73,  180,  190,  207,  217. 
Nobel,  170,  171,  238. 
Nolting,  131,  199. 
Northmore,  174,  231. 
Noyes,  178,  194,  201. 

ODLING,  39,  52. 

Oersted,  141,  233. 

Ogier,  175. 

Olzewski,  174,  241. 

Onnes,  22,  174,  245. 

Ost,  91. 

Ostwald,  57,  177,  181,  182,  183,  187, 

193,  194,  195,  223,  242. 
O'Sullivan,  153. 
Otto,  102,  130. 
Oudemans,  115. 

PAAL,  133. 

Palissy,  164. 

Paracelsus,  9,  29,  62,  65,  209. 

Parker,  158,  245. 

Parkes,  156. 

Parrot,  178. 

Pasteur,    112,    113,    152,    153,    176, 

215,  237. 

Patterson,  no,  115. 
Pattinson,  156. 
Payen,  153,  235. 
Peachey,  115,  116,  244. 
Pebal,  175. 
Pechiney,  158,  241. 
Pelletier,  140,  141,  151,  201,  233. 
PeUigot,    70,    71,    79,  120,  125,  200, 

218,  234. 
Pelouze,    121,    124,    143,  164,    171, 

218. 

Penny,  199. 
Personne,  200. 
Persoz,  153,  235. 
Perkin,  A.  G.,  136,  169,  170,  205. 
Perkin,  F.  M.,  202. 
Perkin,  W.  H.,  Sen.,  91,  103,  122, 

124,    125,    127,    135,    146,   150, 

168,    169,    185,    200,  204,   22O, 

237.  239,  240,  243. 
Perkin,  W.  H.,  Jun.,  93,  94,  95,  118, 

126,    141,    142,    143,   145,   228, 

245- 


INDEX  OF  NAMES 


255 


Peters,  115. 

Petersen,  183,  igo,  igg. 

Petit,  36,  i8g,  igo,  206,  217,  233. 

Pettenkofer,  42,  138,  140. 

Pettersen,  180. 

Pfaff,  125. 

Pfeffer,  177,  178,  180,  240. 

Pfeiffer,  65,  131. 

Philips,  160. 

Piccard,  i6g. 

Pictet,  A.,  140,  141,  245. 

Pictet,  K.,  174,  240. 

Pinner,  102,  106,  133,  141. 

Piria,    7g,  120,    123,  125,  146,  200, 

204,  219,  235. 
Piutti,  150,  242. 
Planta,  141. 
Playfair,  157,  163. 
Pliny,  62,  168. 
Plucker,  184. 
Poggendorff,  233. 
Polis,  130. 
Ponomarew,  151. 

Pope,  115,  116,  17%  223,  244,  245. 
Posselt,  141,  234. 
Precht,  75. 
Priestley,  13,  16,  17,  18,  19,  20,  24, 

25,  26,  62,  70,  71,  197,  202,  205, 

211,  212,  230. 

Pringsheim,  138. 

Proust,   46,    49,    65,  120,  210,  212, 

231,  232. 

Prout,  41,  42,  150,  214,  232,  233. 
Pschorr,  140,  141. 
Ptolemy  Soter,  8. 
Purdie,  113,  114. 

RAMMELSBERG,  68. 

Ramsay,  20,  21,  22,  40,  55,  58,  71, 

174,   180,    183,    186,    207,    223, 

243,  244,  245. 
Raoult,  177,  181. 
Rayleigh,  20,  21,  173,  174,  179,  224, 

243- 

Readman,  158,  245. 
Reaumur,  164,  204. 
Rebuffot,  165. 
Redtenbacher,  150. 
Reformatski,  122. 
Regnault,   81,    121,    140,    141,    174, 

179,  189,  190,  215,  236. 


Reich,  eg. 

Reicher,  196. 

Reimann,  141,  234. 

Reinsch,  120,  200. 

Reinitzer,  175. 

Remsen,  130,  241. 

Retgers,  175,  182. 

Rey,  17,  25,  172. 

Reynolds,  129,  207. 

Richards,  207. 

Richter,  J.  B.,  32,  63,  211,  231. 

Richter,  69. 

Riecke,  186. 

Riedel,  gi. 

Ris,  132. 

Ritter,  188. 

Ritthausen,  146. 

Reberts,  162. 

Robia,  164. 

Robiquet,  141,  153,  234. 

Rochleder,  i6g. 

Rodger,  183. 

Rodziszewski,  132. 

Roebuck,  160,  230. 

Rohde,  141. 

Rome"  de  1'Isle,  175. 

Romer,  165. 

Roosen,  151. 

Rose,  G.,  67. 

Rose,  H.,  46,  65,  70,  201,  202,  217. 

Rosenstiehl,  i6g. 

Roscoe,  54,  62,  65,  70,  157,  186, 188, 

207,  217. 
Rouelle,  13,  63,  128,  150,  210,  229, 

230, 

Roussin,  127. 
Rowland,  186. 
Roozeboom,  195,  196. 
Riicker,  184. 
Rudolph ,  92. 
Riidorff,  181. 
Ruff,  145,  146,  244. 
Riigheimer,  141,  241. 
Runge,  43,  75,  92,    120,    128,    168, 

170,  186,  235. 
Rutherford,  13,  19,  70,  230. 

SABATIER,  118. 
Sabarejew,  179. 
Sachs,  138. 
Sachse,  100. 


256 


A  SHORT  HISTORY  OF  CHEMISTRY 


Salet,  175. 

Sand,  202. 

Sandmeyer,  200. 

Sattler,  168. 

Saussure,  137,  203. 

Sautter,  115. 

Saytzew,  124,  125,  130,  221. 

Scheele,  13,  16,  17,  18,  19,  20,  23, 
25,  62,  64,  65,  66,  69,  70,  71,  76, 
77,  92,  102,  120,  121,  123,  125, 
151,  186,  188,  199,  201,  202, 
211,  230,  231. 

Scheibler,  92,  146,  151,  239. 

Scherer,  145,  176,  237. 

Schiel,  82. 

Schiff,  96,  103,  134,  146,  204. 

Schimmel,  143,  161. 

Schlesmann,  193. 

Schlutius,  163. 

Schmidt,  in,  143. 

Schorlemmer,  54,  169. 

Schonbein,  68,  72,  171,  199. 

Schotten,  204. 

Schraube,  111,  199. 

Schroder,  182. 

Schrotter,  141. 

Schryver,  107. 

Schultze,  150,  188. 

Schulze,  120,  238. 

Schunhardt,  62. 

Schurer,  168. 

Schutze,  187. 

Schiitzenburger,  72. 

Schutzenbach,  161. 

Schwald,  200. 

Schwann,  153,  235. 

Schwarz,  170. 

Schweizer,  143. 

Seebeck,  69. 

Seger,  164. 

Se"guin,  139,  231. 

Selmi,  147. 

Semmler,  142,  143. 

Senarmont,  67. 

Senderens,  118. 

Senebier,  137. 

Serullas,  121,  200,  234. 

Sertuerner,  139,  141,  233. 

Seubert,  207. 

Shenstone,  141. 

Shields,  183,  243. 


Siemens,  156,  164. 

Silber,  94. 

Silbermann,  191. 

Silow,  184. 

Silva,  1 20. 

Simpson,  121,  125. 

Skraup,  132,  134,  140,  141. 

Smiles,  71,  107,  116.  118,  130,  200. 

Sobrero,  121,  171,  236. 

Solomon,  5. 

Solvay,  159,  238. 

Sonnenschein,  140. 

Soret,  72. 

Soubeiran,  71,  121. 

Spilker,  93. 

Spode,  164. 

Sprengel,  182. 

Spring,  72. 

Staedel,  183. 

Stahl,  15,  16,  210. 

Staigmuller,  41. 

Stark,  58,  186. 

Stas,  42,   146,   199,  206,  207,  217, 

235- 

Staudinger,  126. 
Stenhouse,  120. 
Stephen,  143. 

Stewart,  107,  126,  192,  196. 
St.  Gilles,  47,  193,  238. 
St.  Meyer,  184. 
Stohmann,  96. 

Stoney,  Johnstone,  41,  44,  186. 
Streatfield,  126. 
Strecker,   124,    125,    128,   139,   141, 

147,    148,    150,    151,   220,   237, 

238. 

Stromeyer,  69,  156. 
Sudborough,  106. 
Swan,  186. 
Sylvius,  10,  14. 
Synesius,  8. 

TACHENIUS,  10,  201. 
Tafel,  135,  141. 
Talbot,  188. 
Tammann,  175,  180. 
Tanret,  145. 
Tennant,  70,  160. 
Tessie",  165. 
Tessorin,  178. 
Thales,  27. 


INDEX  OF  NAMES 


257 


Thdnard,  60,  62,  65,  71,  72,  84, 
129,  157,  160,  168,  203,  214. 

Theophrastus,  69. 

Thiele,  54,  99,  100,  228,  244. 

Thole,  196. 

Thomas,  156. 

Thomsen,  Julius,  47,  96,  igi,  193, 
216,  237. 

Thomson,  Thomas,  41. 

Thomson,  Sir  J.  J.,  43,  56. 

Thorpe,  73,  183,  184,  207. 

Tickle,  244. 

Tiemann,  122,  123,  142,  143. 

Tilden,  142,  143,  190. 

Tilghman,  164. 

Tollens,  117,  126,  183,  199. 

Traube,  J.,  103,  177,  182. 

Traube,  W.,  149,  151,  244. 

Travers,  22,  244. 

Trouton,  183. 

Tschitschibabin,  119. 

Tschugaew,  114,  115,  224. 

ULRICH,  75. 
Unger,  151,  236. 
Unverdorben,  128,  233. 
Urbain,  73,  201. 
Ure,  171,234. 

VALENTINE,  Basil,  9,  23,  29,  62,  64, 

65,  69,  70,  120,  198,  201. 
Van  der  Plaats,  207. 
Van  der  Waals,  173,  179,  182,  206, 

224,  241. 

Van  Deventer,  196. 
Van  Grote,  126. 
Van  Helmont,  10,  17,  19,  20,  23,  62, 

64.  65,  76,  117,  152,  170,  172, 

202,  209. 

Van  Than,  129,  239. 
Van   't   Hoff,  48,  67,  94,  100,  108, 

no,  112,    113,    115,   125,   126, 

177,   178,   180,    191,    194,  195, 

196,  224,  240,  241. 
Varrentrapp,  203. 
Vaubel,  100. 
Vaudin,  161. 
Vauquelin,  66,  69,  70,  125,  137,  150, 

213,  231,  232,  233. 
Veley,  205. 
Veraguth,  94,  245. 

17 


Verguin,  169,  237. 

Vernet,  181. 

Vernon,  184. 

Vieille,  171,  189,  242. 

Villiger,  143. 

Vogel,  187. 

Voget,  143. 

Voit,  138,  139. 

Volckel,  143. 

Volhard,   133,    150,    151,   205,   222, 

239. 

Volta,  49,  178. 
Vongerichten,  141. 
Von  Pechmann,  92,  118,  123,  127, 

128,  228,  243. 
Von  Reichenstein,  70. 

WAAGE,  47,  48,  192,  239. 

Wackenroder,  72. 

Wagemann,  161. 

Wagner,  142,  143,  157. 

Wanklyn,  169. 

Walden,    113,   114,   115,    177,  178, 

184,  224,  243,  245. 
Walker,  J.  W.,  178,  194. 
Walker,  41,  177,  192,  193,  224. 
Wallach,  142,  143,  228. 
Walz,  146. 
Warburg,  22,  189. 
Waterson,  173,  236. 
Watson,  70,  230. 
Weber,  71,  190. 
Wedgwood,  164. 
Weidel,  140. 
Weil,  132. 
Weith,  91,  102. 
Weldon,  158,  239,  241. 
Welsbach,  73,  158,  167,  241. 
Welter,  120,  169,  231. 
Weltner,  200. 
Wenzel,  45,  192,  230. 
Werner,  54,  55,  65,    no,  HI,  175, 

•*a*r  242. 
Wertheim,  129. 
Weselsky,  169,  201. 
Whiteley,  114. 
Whitney,  178. 
Wiedemann,  189. 
Wiggers,  143. 
Wiis,  178. 
Wilhelmy,  47,  153,  193,  194,  237. 


258         A  SHORT  HISTORY  OF  CHEMISTRY 


Wildemann,  188. 

Wilsmore,  126,  192,  245. 

Will,  146,  203,  238. 

Willgerodt,  115. 

Williams,  143. 

Williamson,  52,  57,  84,  85,  86,  120, 

121,  220,  237. 
Willstatter,  94,  138,  140,  141,  228, 

244,  245. 

Winkelblech,  178. 
Winkler,  70,  160,  165,  205,  207,  217, 

240. 

Winsor,  167. 
Wislicenus,  J.,  94,  109,  112,119, 122, 

124,  125,  228,  240. 
Wislicenus,  W.,  71,  103,  104. 
Witt,  187. 
Wittorf,  143. 
Wohl,  145,  146,  243. 
Wolffenstein,  72. 
Woskresorski,  123,  151. 
Wolf,  126. 
Wolter,  165. 
Wohler,  3,  62,  65,  68,  69,  71,  72,  77, 

78,  80,  86,  102,  120,   122,  123, 


124,  125,    128,    130,    137,    139, 
141,    146,    147,    150,    151,  157, 

163,  197,  202,  2l8,  233,  234. 

Wollaston,  35,   70,    150,    186,   187, 

213,  231,  232. 
Wray,  125. 
Wright,  141. 

Wroblewski,  95,  174,  241. 
Wurtz,  51,  52,  71,  73,  84,  85,  86,  92, 

Il8,     119,     122,     127,     151.     219, 
236,  237,  239,  240. 

YOSHIDA,  143. 

Young,  S.,  174,  180,  224. 
Young,  T.,  182. 

ZEISE,  129. 

Zeisel,  141,  201,  204. 

Zelinsky,  94,  245. 

Zincke,  144,  241. 

Zinin,  127,  128,  170,  199,  219,  236. 

Zogoumenny,  199. 

Zosimos  of  Panopolis,  8. 


INDEX  OF  SUBJECTS 


ACETOACETIC  ester,  101. 

Acetyl  theory  (Liebig),  79. 

Acid  amides  and  anilides,  organic, 

124,  151. 
Acid    anhydrides     and      peroxides, 

organic,   124. 

Acid  chlorides,  organic,  124. 
Acids,  13,  50,  59,  62,  71,  122-5,  145- 

5i. 

—  amido,    detailed    summary    of, 

114,  125,  145,  147,  150. 

—  carboxylic,  detailed  summary  of, 

122,  125. 

—  detailed  summary  of,  62,  71. 

—  ethylenic,  detailed  summary  of, 

124,  125. 

—  hydroxy,  detailed  summary  of, 

124,  125. 

—  ketonic,   detailed  summary   of, 

126. 

—  polybasicity  of,  52,  61. 
Affinity,  chemical,  45. 

—  residual,  54. 
Agricultural  chemistry,  138. 
Air,  nature  of,  16,  17. 
Albumens,  147. 
Alchemy,  medicinal,  4,  7,  9. 

—  transmutational,  4,  6,  7. 
Alcohols,  detailed  summary  of,  119, 

120. 

Alcohol,  technical  methods,  160,  161. 
Aldehydes,    detailed    summary    of, 

121,  123. 

Alexandrian  Academy,  the,  8. 
Alkalies,  64. 

—  electrotechnical      methods     of 

preparation,  157,  158,  159. 
Alkaloids,    detailed    summary    of, 
119,  120. 


Allotropy,  68. 

Amido-compounds,  organic,  detailed 

summary  of,  127,  128. 
Ammonium    bases,    organic    (Hof- 

mann),  84,  85. 
Analysis,  gas,  205. 

—  inorganic  qualitative,  201. 
quantitative,  201. 

—  mineral,  66,  201. 

—  of  alkaloids,  140. 

—  of  sugar,  144. 

—  organic  qualitative,  202. 
quantitative,  203. 

—  spectrum,  21,  68,  157. 

—  volumetric,  204. 
Animal  chemistry,  137. 
Antimony,   organic    derivatives    of, 

129. 
Apparatus,   improvements    in,    197, 

198. 

Arabs,  chemistry  of,  8. 
Arsenic,  organic  derivatives  of,  129. 
Atom,  definition  of  (Laurent),  38,  81. 
Atomic  theory  (Dalton),  32-4. 

—  weight    confusion    (1830-1850), 

—  weights,       determination       of 

(Berzelius),  35,  206. 

(Cannizzaro),  38,  206. 

(Dumas  and   Marignac), 

206. 

(modern),  206-7. 

(Stas),  42. 

(summary),  207. 

mathematical  regularities  in, 

42-4. 

"  BARRED  SYMBOLS  "  (Berzelius),  31. 
Bases,  13,  50,  52. 


260         A  SHORT  HISTORY  OF  CHEMISTRY 


Bases,  detailed  summary  of,  64. 
Benzene,  physical  properties  of,  96. 

—  space    formula    for   (dynamic), 

98,  100. 
(static),  97,  99,  100. 

—  theory,  88-90,  94-6,  113. 
Boiling-point,  183,  184. 

elevation    of     (Beckmann), 

181. 

CARBIDES,  163. 

Carbon  atom,  tetrahedral  (Le  Bel- 

van't  Hoff),  108,  112. 
Carbonic  acid,  Black  on,  18,  64. 

nature  of,  19,  62. 

Catalysis,  194. 

Cathode  rays,  43. 

Cements,  164, 165. 

Chemical    methods,    improvements 

in,  198-201. 
Chemical  statics  and  dynamics,  48, 

192-5. 

Chemistry,  origin  of  name,  6. 
Chinese,  chemistry  of,  i,  3,  5. 
Chlorine,  elementary  nature  of,  60. 

—  technical  preparation  of,  158. 
Christianity  in  relation  to  chemistry, 

6,  8,  9. 
Classification  of  organic  compounds 

(Gerhardt,  Laurent),  82,  86. 
Clays,  164. 

Coal-tar  products,  167,  168. 
Colloids,  178,  179. 
Colour,  theories  of,  187. 
Combustion  and  respiration,  analogy 

between,  14. 

—  Lavoisier's  theory  of,  3,  24,  26, 

166. 

—  phlogistic  theory  of,  2,  12,  15, 

16. 
Condensation,  aldol,  122. 

—  benzoin,  122. 

—  Claisen,  122. 

—  Knoevenagel's,  126, 

—  of    malonic     and    acetoacetic 

esters,  126. 

—  Michael's,  126. 

Constant     combining     proportions, 

law  of,  46,  49. 

Controversy,  Proust-Berthollet,  46. 
Copulated  compounds,  82,  83. 


Critical  phenomena  of   gases  and 

liquids,  174. 

Crystallography,  66,  175. 
Crystals,  liquid,  175. 
Cyclic  compounds,  conjugated  car- 
bocyclic,    detailed    summary 
of,  93- 

heterocyclic,   detailed  sum- 
mary of,  91,  92,  131-6. 

reduced  carbocyclic,  detailed 

summary  of,  94,  118. 

DESMOTROPY,  101. 
Diazo-compounds,  detailed  summary 
of,  128. 

isomeric,  in. 

Dielectric  constant,  184. 
Diffusion,  178. 

Diketones,  detailed  summary  of,  123. 
Dispersive  power,  185. 
Dissociation,  174,  175. 
Dyestuffs,  5,  167. 

—  detailed  summary  of,  168-70. 

EGYPTIANS,  chemistry  of,  2,  3,  5. 
Electrical  conductivity,  177,  178. 

of  acids,  177. 

of  pure  water,  177. 

Electric  furnace,  158. 
Electrochemical  theory  of  Arrhenius 
and  Faraday,  57. 

(dualistic)  of  Berzelius,   31, 

50,  51,  56,  60,  61,  63,  66. 

of  Clausius,  56. 

(dualistic)     of     Davy     and 

Volta,  49,  56,  76. 

of  Grotthus,  56. 

Electrochemistry,   theories  of,    191, 

192. 
Electrolysis,  hydrate   theory  of,  58. 

—  laws  of,  51. 

Electrolytes,  amphoteric,  178. 
Electronic  theory,  44,  56,  58. 
Electrons,  43. 
Electrotechnical  methods,  154,  156, 

157,  158,  159,  162,  163. 
Elements,  alchemical,  14,  28. 

—  Aristotelian,  14,  27. 

—  Boyle's  definition  of,  29,  32. 

—  detailed  summary  of,  69,  70. 
Enzymes  and  enzyme  action,  152. 


INDEX  OF  SUBJECTS 


261 


Epochs,  chief  chemical,  i. 
Equivalent  combining  proportions, 
law  of,  32. 

—  definition  of  (Laurent),  38,  52, 

81. 

Esterification,  47,  193. 
Esters,  detailed  summary  of,  121. 
Ether  and  alcohol,  relation  between 

(Williamson),  84. 
Etherin  theory  (Dumas  and  Boullay), 

79- 

Ethers,  detailed  summary  of,  119. 
Ethylenic     compounds,     stereoiso- 

meric,  109. 
Eutectic  point,  196. 
Explosives,  170,  171. 

FERMENTATION,  theories  of,  152, 

Fluorescence,  187. 

Freezing-point,        depression        of 

(Raoult),  181. 
Furfurane  compounds,  92,  133,  136. 

GASES,  for  heating  purposes,  166. 

—  liquefaction  of,  21,  174. 

—  •  physical   investigation    of,    13, 

172-4. 

—  the  inert,  20,  2,1,  40. 
Gas-lighting,     technical     improve- 

ments in,  158,  167. 
Glass,  5,  163. 
Glucosides,  142,  146. 
Greeks,  chemistry  of,  2,  6. 
Grignard's  reaction,    119,   121,  122, 


HALIDES  of  non-metallic  elements, 

72. 
Halogens,  60. 

—  compounds,  organic,  200. 
Heat  of  chemical  combination,  190. 

—  technical  methods,  166. 
Hemihedry,  176. 
Hindus,  chemistry  of,  i,  5. 
Hydrazine     derivatives,       detailed 

summary  of,  128. 
Hydrides  of  the  elements,  71. 
--  nitrogen  group,  71. 
Hydrocarbons,  detailed  summary  of, 

117. 
Hydrogen,  nature  of,  23,  24. 


Hydrolysis,  193,  200. 
Hygienic  chemistry,  138. 
Hypothesis,  Avogadro's,  35,  173. 

—  Prout's,  41. 

ILLUMINANTS,  166. 
India  rubber  industry,  165. 
Indicators,  theory  of,  205. 
Inductive    reasoning,     applied    to 

chemistry,  2,  n,  12. 
Inorganic  compounds,  structure  of, 

49- 

Internal  friction,  183,  196. 
Ionic  theory  of  Arrhenius,  57,  61. 
Isomerism,  68,  77. 

—  dynamic,  100-5. 

—  geometrical,  107-11. 

—  optical,  111-16. 
Isomorphism,  Mitscherlich's  law  of, 

49. 
Isonitriles,    detailed    summary     of, 

128. 
Isonitroso      compounds,      detailed 

summary  of,  129. 
Isoquinoline  compounds,  135,  136. 

JEWS,  chemistry  of,  3. 

KETEN,  126. 

Ketones,  detailed  summary  of,  121, 

123. 
Kinetic  theory  of  gases,  173. 

LATENT  heat,  190. 

MAGNETIC  rotation,  185,  186. 

Magnetism,  184. 

Mass-action,  law  of,  45,  47,  48. 

Matches,  165. 

Melting-point,  183. 

Meta  elements  (Crookes),  73. 

Metal  alkyls,  detailed  summary  of, 

130. 

Metallammine  compounds,  54. 
Metallurgy,  5,  154-6. 
Metallurgy  of  iron  and  steel,  155-7. 
Metals  of  the  rare  earths,  73. 
Meteorites,  68. 
Mineralogy,  65. 
Molecular  dispersive  and  refractive 

power,  96,  103,  185,  193. 


262         A  SHORT  HISTORY  OF  CHEMISTRY 


Molecular  magnetic  rotatory  power, 
103,  185,  186. 

—  volume,  96,  182. 

—  weight,  physical  determination 

of,  179-81. 

Molecule  and  molecular  weight,  de- 
finitions of  (Laurent),  38,  81. 

Morphotropy,  176. 

Multiple  combining  proportions, 
law  of,  33,  49. 

NlTRILES,  124. 

Nitro      and      nitroso     compounds, 

organic,  127,  171,  199. 
Nitrogen,  discovery  of,  19. 

—  fixation    of    atmospheric,    155, 

162,  163. 

—  optically  active,  115. 

—  technical  preparation  of,  158. 
Nomenclature    of     chemical    com- 
pounds, 30,  60. 

Notation,  chemical  (Berzelius),  31, 

32. 
(Dalton),  32. 

—  modern  structure,  53,  87,  88. 
Nucleus  theory  (Laurent),  80. 

OCTAVES,  law  of  (Newlands),  39. 
Optical  activity  and  ring- formation, 
114. 

—  and  unsaturation,  115. 

—  of  electrolytes,  115. 

—  of  homologous  series,  114. 

—  quantitative  theory,  113. 
Organic  chemistry,  13,  76,  117,  137. 
Osmotic  pressure,  177. 

measurement  of,  180,  181. 

Oxidation,  electrolytic,  192. 

—  of  organic  compounds,  199. 
Oxides  and  oxy-acids  of  nitrogen, 

phosphorus  and  sulphur,  71. 
Oximes,  detailed  summary  of,  129. 

—  stereo-isomeric,  109,  no. 
Oxygen,  discovery  of,  18. 

—  technical  preparation  of,  158. 

PAPER,  165. 

Periodic  system  of  elements,  38-41, 

53- 

anomalies  of,  40,  208. 

(Benedicks),  74. 


Peroxide  of  hydrogen  and  per- acids, 

72. 

Phase  rule,  195. 

Phenols,  detailed  summary  of,  120. 
Phlogistic  chemists,  12. 
Phoenicians,  chemistry  of,  3,  5. 
Phosphorus,  organic  compounds  of, 

129. 

Photo-chemistry,  187-189. 
Physical   properties,    additive,   con- 
stitutive, colligative,  181. 

and    chemical    constitution, 

relations  between  (electrical), 
184. 

(mechanical),  181-4. 

—  (optical),  185-189. 

(thermal),  189-91. 

Polyketides,  126. 

Polymerism,  68,  77. 

Polymorphism,  68,  176. 

Pottery,  5,  154,  164. 

Proteins,  145,  148. 

Purines,  145,  149,  151. 

Pyridine  compounds,  91,   133,  134, 

136. 

Pyrone  compounds,  91,  136,  170. 
Pyrrol  compounds,  92,  133,  136. 

QUADRIVALENCY  of  carbon,  87. 
Quinoline  compounds/gi,  132-4, 136. 
Quinones,  detailed  summary  of,  123. 

RADICLE      theories       in      organic 

chemistry,  78,  83,  86. 
—  theory,  Liebig's  first,  78. 

Radioactive  elements,  75. 

Radioactivity,  23. 

Rate  of  reaction,  193,  194. 

Reduction  of   organic    compounds, 
118,  199. 

Reduction,  electrolytic,  191. 

Refractive  power,  185. 

Romans,  chemistry  of,  6. 

SALTS,  inorganic,  13,  32,  50,  62,  63. 
Salts,  inorganic,  detailed  summary 

of,  64,  65. 

Saturation  capacity,  86. 
Selenium,  optically  active,  116. 
Silicon  compounds,  organic,  detailed 

summary  of,  130. 


INDEX  OF  SUBJECTS 


263 


Silicon,  optically  active,  116. 
Soap,  manufacture  of,  162. 
Societies,  alchemical,  10. 
Soda  manufacture,  159. 
Solution,  theories  of,  176,  177. 
Specific  atomic  heat,  36,  189. 
Specific  gravity  and  specific  volume, 

182. 

Specific  heat  of  gases,  189. 
of  elements  and  compounds, 

189,  190. 
Spectra    absorption,    96,    104,    187, 

193,  196. 

—  of  elements,  43,  186. 
Spectroscopy,  186,  187. 
Steric  hindrance,  105-7. 
Structural   theory,   modern,    in   or- 
ganic chemistry,  78,  86,  87. 

Substitution,  51,  80,  166. 

Sugars,  142,  144,  146. 
—  technical  preparation  of,  161. 

Sulphonation  and  sulphination,  200. 

Sulphur,  optically  active,  116. 

Sulphur  compounds,  organic,  de- 
tailed summary  of,  129,  130. 

Sulphuric  acid,  manufacture  of,  155, 
160. 

Surface  tension,  182. 

Synthesis,  asymmetric,  114. 

—  electric,  192. 

—  of  alkaloids,  140,  141. 

—  of   amido-acids    and    proteins, 

147,  148,  150. 

—  of  hydrocarbons,  118. 

—  of  organic  dyestuffs  (technical), 

155- 

—  of  purines,  149,  151. 
-  of  sugars,  144,  146. 

—  of  terpenes,  142,  143. 

—  of  vegetable  and  animal  pro- 

ducts, 139. 

TAUTOMERIC  compounds,  detailed 
summary  of,  102,  103. 

Tautomerides,  physical  properties 
of,  103,  104. 


Tautomerism,  100. 

—  theories  of,  104,  105. 
Technical  chemistry,  13. 
Terpenes,  detailed  summary  of,  140, 

142,  143. 

—  technical  preparation  of,  161. 
Theory  of  residues  (Gerhardt),  81. 
Thermite     process     (Goldschmidt), 

158. 
Thermo-chemistry,  96,  189-91,  193. 

—  of  explosives,  170. 
Thiophene  compounds,  92, 133, 136. 
Tin,  optically  active,  116. 
Transmutation  of  metals,  2,  5. 
Type  theories  in  organic  chemistry, 

52,  78,  80,  84,  86. 
Type  theory,  mechanical  (Dumas), 

81. 
Types,  four  general  (Gerhardt),  82, 

86. 
Types,  mixed  (Williamson),  85,  86. 

UNSATURATION,  conjugated,  54. 
Urea,  derivatives  of,  detailed  sum- 
mary, 128,  150,  151. 

VALENCY,  51-6,  85,  86,  88. 

—  and  the  electronic  theory,  56. 

—  "normal"  and  "contra,"  55. 

—  Werner's  theory,  54. 
Vapour-density  determination  (Du- 
mas), 37,  179- 

Hofmann),  180. 
Victor  Meyer),  180. 
Regnault,  etc.),  179. 

—  —  theory,  179. 
Vapour-pressure  curves,  196. 
Vegetable  chemistry,  137. 
Vinegar,  manufacture  of,  161. 
Vital     force     theory     of     organic 

chemistry,  77. 
Volumes,  Gay-Lussac's  law  of,  33, 
35.  173. 

WALDEN  inversion,  113. 
Water,  nature  of,  16,  23,24. 


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